Packaging material for battery

ABSTRACT

Disclosed is a packaging material for forming an armor body for a battery, the armor body being adapted for use in such a manner that a battery body is inserted into the armor body and the peripheral edge of the armor body is then heat sealed for hermetic sealing, the packaging material being a laminate comprising at least a substrate layer, an adhesive layer, a barrier layer, a dry laminate layer, and a sealant layer, characterized in that at least the sealant layer comprises a low-fluidity polypropylene layer having low susceptibility to collapse upon exposure to heat and pressure at the time of heat sealing and a high-fluidity polypropylene layer having high susceptibility to collapse upon exposure to heat and pressure at the time of heat sealing, and the innermost layer is the high-fluidity polypropylene layer. This battery packaging material can impart moisture barrier properties and resistance to contents of the battery.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a packaging material for abattery, which has moisture barrier properties and resistance tocontents of the battery and is usable for batteries with a liquid orsolid organic electrolyte (polyelectrolyte), fuel batteries (cells),capacitors and the like.

[0003] 2. Background Art

[0004] The term “battery” as used in the present invention refers toobjects including devices for converting chemical energy to electricenergy, for example, lithium ion batteries, lithium polymer batteries,and fuel batteries, or electrolytic capacitors containing liquids, solidceramics, organic materials or other dielectric materials, for example,liquid capacitors, solid capacitors, and bilayer capacitors.

[0005] Batteries are used for applications such as personal computers,portable terminal devices (for example, portable telephones (cellularphones) and PDA), video cameras, electric automobiles, energy storagebatteries, robots, and satellites.

[0006] Metal cans produced by pressing metals to form cylindrical orrectangular parallelepiped vessels, or bags formed from a laminate of acomposite film produced by lamination of plastic films, metal foils andthe like (hereinafter referred to as “armor body”) have hitherto beenused as the armor body for the above batteries.

[0007] The conventional armor bodies for batteries, however, have thefollowing problems. In metal cans, since the outer wall of the vessel isrigid, the shape of the battery per se is disadvantageously limited. Forthis reason, since the hardware side is designed according to thebattery, the dimension of the hardware used in the battery isdisadvantageously determined by the battery and, thus, the degree offreedom in shape is reduced.

[0008] For this reason, the above bag-like armor body is generally used.From the viewpoints of properties required of batteries, moldability orfabricability, profitability and the like, the material for the armorbody comprises at least a substrate layer, a barrier layer, a sealantlayer, and an adhesive layer for bonding the above layers to each other,and an intermediate layer is optionally provided.

[0009] A pouch is formed from a laminate having the above constructionfor a battery, or alternatively at least one side of the laminate issubjected to press molding to form a housing part for a battery. Abattery body is housed in the pouch or the housing part, and, in thepouch type or the emboss type (covered with a lid), the necessary partof the peripheral edge thereof is heat sealed for hermetic sealing toprepare a battery.

[0010] The innermost layer in the sealant layer should have heat sealingproperties between the innermost layers and, in addition, should haveheat sealing properties on leads (metals). For example, the use of anacid-modified polyolefin resin having adhesion to metals in theinnermost layer can ensure the adhesion to leads.

[0011] A. Stacking the acid-modified polyolefin resin as the innermostlayer in the armor body, however, is disadvantageous, for example, inthat, as compared with general polyolefin resins, the moldability orfabricability is inferior and, in addition, the cost is higher. For thisreason, a method has hitherto been adopted wherein a general polyolefinresin layer is used as the innermost layer of the sealant layer in thearmor body and a film for a lead, which is heat bondable to both theinnermost layer and the lead, is interposed in the lead part.

[0012] More specifically, as shown in FIG. 1G(a), a film 6′ for a lead,which has heat sealing properties on both a metal and a sealant layer inthe armor body, is interposed between a lead 4 and a sealant layer 14′in a laminate 10′ to ensure hermetic sealing properties in the leadpart.

[0013] A film of the above unsaturated carboxylic acid-graftedpolyolefin, a metal-crosslinked polyethylene, or a copolymer of ethyleneor propylene with acrylic acid or methacrylic acid may be used as thefilm for a lead.

[0014] The sealant layer in the laminate for constituting the armor bodyfor a battery (hereinafter referred to as “armor body”) is formed ofpolypropylene, for example, from the viewpoints of heat resistance andhermetic sealing properties. In this case, a polypropylene resin, whichexhibits good hermetic sealing properties and is likely to be collapsedupon heating and pressing at the time of heat sealing, that is, apolypropylene resin having a large melt index (hereinafter referred toas “MI”), is used. An acid-modified polypropylene film is used as thefilm for a lead. Upon hermetic heat sealing using the packaging materialfor a battery having the above construction and the film for a leadhaving the above construction, as shown in FIG. 1G(b), both the heatseal layer 14′ in the armor body and the film layer 6′ for a lead aremelted, at a portion where the lead exists, by heat and pressure forheat sealing and, further, upon pressing, are often extruded to theoutside of the region of the pressing part. As a result, the aluminumfoil as the barrier layer 12′ in the armor body 10′ often comes intocontact (S) with the metal lead 4′, resulting in short-circuiting.

[0015] Further, as shown in FIGS. 1H(a) to 1H(c), upon heat sealing ofthe peripheral edge of the armor body, microcracks (hereinafter referredto as “root cutting C”) often occur in the sealant layer in its portionnear the inner edge of the sealed part. Upon root cutting, anelectrolysis solution comes into direct contact with the barrier layer.As a result, insulation among the battery body, the metal of the lead,and the barrier layer is broken, and a potential difference occurs. Thepotential difference results in the formation of throughholes due to thecorrosion of the barrier layer and the formation of a reaction productof a metal ion as the electrolyte called “dendrite.” These unfavorablephenomena shorten the service life of the battery.

[0016] B. Further, stacking the acid-modified polyolefin resin as thesealant layer in the armor body or the innermost layer in the sealantlayer is disadvantageous, for example, in that, as compared with generalpolyolefin resins, the moldability or fabricability is inferior and, inaddition, the cost is higher. For this reason, a method has hithertobeen adopted wherein a general polyolefin resin layer is used as thesealant layer in the armor body or the innermost layer in the sealantlayer and a film for a lead, which is heat bondable to both the sealantlayer or the innermost layer in the sealant layer and the lead, isinterposed in the lead part.

[0017] More specifically, as shown in FIG. 2G(a), a film 6′ for a lead,which has heat sealing properties on both a metal lead and a sealantlayer in the armor body or the innermost layer in the sealant layer, isinterposed between a lead 4 and a heat seal layer 14′ in a laminate 10′to ensure hermetic sealing properties in the lead part.

[0018] A film of the above unsaturated carboxylic acid-graftedpolyolefin, a metal-crosslinked polyethylene, or a copolymer of ethyleneor propylene with acrylic acid or methacrylic acid may be used as thefilm for a lead.

[0019] The sealant layer or the innermost layer in the sealant layer inthe laminate for constituting the armor body for a battery (hereinafterreferred to as “armor body”) is formed of polypropylene, for example,from the viewpoints of heat resistance and hermetic sealing properties.In this case, a polypropylene resin, which exhibits good hermeticsealing properties and is likely to be collapsed upon heating andpressing at the time of heat sealing, that is, a polypropylene resinhaving a large melt index (hereinafter referred to as “MI”), is used. Anacid-modified polypropylene film is used as the film for a lead. Uponhermetic heat sealing using the packaging material for a battery havingthe above construction and the film for a lead having the aboveconstruction, as shown in FIG. 2G(b), both the heat seal layer 14′ inthe armor body and the film layer 6′ for a lead are melted, at a portionwhere the lead exists, by heat and pressure for heat sealing and,further, upon pressing, are often extruded to the outside of the regionof the pressing part. As a result, the aluminum foil as the barrierlayer 12′ in the armor body 10′ often comes into contact (S) with themetal lead 4′, resulting in short-circuiting.

[0020] Further, as shown in FIGS. 2H(a) to 2H(c), upon heat sealing ofthe peripheral edge of the armor body, microcracks (hereinafter referredto as “root cutting C”) often occur in the sealant layer in its portionnear the inner edge of the sealed part. Upon root cutting, anelectrolysis solution comes into direct contact with the barrier layer.As a result, insulation among the battery body, the metal of the lead,and the barrier layer is broken, and a potential difference occurs. Thepotential difference results in the formation of throughholes due to thecorrosion of the barrier layer and the formation of a reaction productof a metal ion as the electrolyte called “dendrite.” These unfavorablephenomena shorten the service life of the battery.

[0021] C. Further, stacking the acid-modified polyolefin resin as thesealant in the armor body is disadvantageous, for example, in that, ascompared with general polyolefin resins, the moldability orfabricability is inferior and, in addition, the cost is higher. For thisreason, a method has hitherto been adopted wherein a general polyolefinresin layer is used as the sealant layer in the armor body and a filmfor a lead, which is heat bondable to both the sealant layer and thelead, is interposed in the lead part.

[0022] Further, in the packaging material for a battery, comprising thesubstrate layer, the barrier layer, the adhesive resin layer, and thesealant layer, when the sealant layer is formed of, for example, apolypropylene resin, the adhesive resin layer in the laminate of thebarrier layer and the sealant layer is formed of acid-modifiedpolypropylene.

[0023] An acid-modified polyolefin with a large MI value having goodprocessability is used as the adhesive resin layer in the laminate forconstituting the armor body for a battery (hereinafter referred to as“armor body”). The acid-modified polyolefin having a large MI value,however, is a resin which is likely to be collapsed upon exposure toheat and pressure at the time of heat sealing. Upon hermetic heatsealing using the packaging material for a battery having theconstruction using the above adhesive resin layer, as shown in FIG.3G(b), all of the adhesive resin layer and the sealant layer 14′ in thearmor body and the film layer 6′ for a lead are melted, at a portionwhere the lead exists, by heat and pressure for heat sealing and,further, upon pressing, are often extruded to the outside of the regionof the pressing part. As a result, the aluminum foil as the barrierlayer 12′ in the armor body 10′ often comes into contact (S) with themetal lead 4′, resulting in short-circuiting.

[0024] Further, as shown in FIGS. 3H(a) to 3H(c), upon heat sealing ofthe peripheral edge of the armor body, very small root cutting C oftenoccurs in the adhesive resin layer and the sealant layer in theirportion near the inner edge of the sealed part. Upon the occurrence ofroot cutting, an electrolysis solution comes into direct contact withthe barrier layer. As a result, insulation among the battery body, themetal of the lead, and the barrier layer is broken, and a potentialdifference occurs. The potential difference results in the formation ofthroughholes due to the corrosion of the barrier layer and the formationof a reaction product of a metal ion as the electrolyte called“dendrite.” These unfavorable phenomena shorten the service life of thebattery.

[0025] D. Further, a pouch-type armor body, in which a laminate isformed into a bag and a battery body is housed in the bag, or anemboss-type armor body, in which the laminate is press molded to form aconcave portion and a battery body is housed in the concave portion, hasbeen developed. As compared with the pouch type, the emboss type canprovide a more compact package. In any type of armor body, for example,moisture barrier properties as a battery, strength such as piercingresistance, and insulating properties are indispensable in the armorbody for a battery.

[0026] The packaging material for a battery is a laminate comprising atleast a substrate layer, a barrier layer, and a sealant layer. It hasbeen confirmed that the interlaminar bonding strength among the abovelayers affects properties required of the armor body of the battery. Forexample, unsatisfactory bonding strength between the barrier layer andthe sealant layer is causative of the entry of water from the exterior.The entry of water causes the corrosion of the aluminum face byhydrofluoric acid produced by a reaction of the electrolyte in thecomponents constituting the battery with the above water andconsequently causes delamination between the barrier layer and thesealant layer. Further, in the formation of the emboss-type armor body,at the time of press molding of the laminate to form a concave portion,delamination between the substrate layer and the barrier layer oftenoccurs.

[0027] Further, when a resin having a high tensile modulus of elasticityis used in the sealant layer, at the time of emboss molding, the sealantlayer often undergoes whitening or slight cracking in its surface.Further, the molding stability is poor, and pinholes, molding wrinkling,or cracks often occur.

[0028] Furthermore, hermetical sealing properties after filling of thecontents and sealing may be mentioned as properties which areindispensable as the packaging material for a battery. For example, whenthe seal strength of the packaging material is low, a satisfactory timeis necessary for sealing in a content filling/sealing line. Thissignificantly hinders cycle shortening and often deteriorates theproduction efficiency.

SUMMARY OF THE INVENTIO

[0029] A. First Aspect of the Invention

[0030] The present inventors have now found that a packaging material,for a battery, for forming an armor body adapted for use in such amanner that, in packaging of a battery, a battery body is inserted intothe armor body using a polypropylene resin as a sealant layer and theperipheral edge of the armor body is heat sealed for hermetic sealing,can be provided which can prevent short-circuiting between a barrierlayer in the armor body and a lead upon the application of heat andpressure necessary for the heat sealing and does not have any fear ofcausing root cutting in the sealant layer, that is, has excellentinsulating properties and has stable hermetic sealing properties.

[0031] Thus, according to the first aspect of the present invention,there is provided a packaging material for forming an armor body for abattery, said armor body being adapted for use in such a manner that abattery body is inserted into the armor body and the peripheral edge ofthe armor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, a barrier layer, a dry laminate layer, and a sealantlayer, characterized in that

[0032] at least the sealant layer comprises a low-fluidity polypropylenelayer having low susceptibility to collapse upon exposure to heat andpressure at the time of heat sealing and a high-fluidity polypropylenelayer having high susceptibility to collapse upon exposure to heat andpressure at the time of heat sealing, and the innermost layer is thehigh-fluidity polypropylene layer.

[0033] B. Second Aspect of the Invention

[0034] The present inventors have now found that a packaging material,for a battery, for forming an armor body adapted for use in such amanner that, in packaging of a battery, a battery body is inserted intothe armor body using a polypropylene resin as a sealant layer and theperipheral edge of the armor body is heat sealed for hermetic sealing,can be provided which can prevent short-circuiting between a barrierlayer in the armor body and a lead upon the application of heat andpressure necessary for the heat sealing and does not have any fear ofcausing root cutting in the sealant layer, that is, has excellentinsulating properties and has stable hermetic sealing properties.

[0035] Thus, according to the second aspect of the present invention,there is provided a packaging material for forming an armor body for abattery, said armor body being adapted for use in such a manner that abattery body is inserted into the armor body and the peripheral edge ofthe armor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, a barrier layer, an adhesive resin layer, and a sealantlayer, characterized in that

[0036] at least the sealant layer comprises a low-fluidity polypropylenelayer having low susceptibility to collapse upon exposure to heat andpressure at the time of heat sealing and a high-fluidity polypropylenelayer having high susceptibility to collapse upon exposure to heat andpressure at the time of heat sealing, and the innermost layer is thehigh-fluidity polypropylene layer.

[0037] C. Third Aspect of the Invention

[0038] The present inventors have now found that a packaging material,for a battery, for forming an armor body adapted for use in such amanner that, in packaging of a battery, a battery body is inserted intothe armor body and the peripheral edge of the armor body is heat sealedfor hermetic sealing, can be provided which can prevent short-circuitingbetween a barrier layer in the armor body and a lead upon theapplication of heat and pressure necessary for the heat sealing and doesnot have any fear of causing root cutting in the sealant layer, that is,has excellent insulating properties and has stable hermetic sealingproperties.

[0039] Thus, according to the third aspect of the present invention,there is provided a packaging material for forming an armor body for abattery, said armor body being adapted for use in such a manner that abattery body is inserted into the armor body and the peripheral edge ofthe armor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, aluminum, a conversion treated layer, an adhesive resinlayer, and a polypropylene resin-based sealant layer, characterized inthat the adhesive resin layer is formed of a resin having a melt indexin the range of 5 to 20 g/10 min.

[0040] D. Fourth Aspect of the Invention

[0041] The present inventors have now found that a production processcan be provided for a packaging material, for a battery, which has goodbattery body protecting properties and can realize highly productiveemboss molding process, a content filling/sealing process and otherprocesses.

[0042] Thus, according to the fourth aspect of the present invention,there is provided a packaging material for forming an armor body for abattery, said armor body being adapted for use in such a manner that abattery body is inserted into the armor body and the peripheral edge ofthe armor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer 1, a barrier layer, an adhesive layer 2, and a sealantlayer, characterized in that

[0043] the sealant layer comprises one resin layer or a laminate of twoor more resin layers comprising metallocene linear low-densitypolyethylene.

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Drawings

[0045]FIG. 1A is a diagram illustrating a packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing the layer construction of a packagingmaterial for a battery and the positional relationship among thepackaging material, a film for a lead, and a lead, (b) a cross-sectionalview illustrating the state of contact among the lead, the film for alead, and an armor body before heat sealing at the lead part, (c) atypical cross-sectional view of the lead part after heat sealing, and(d), (e), and (f) the same explanatory views as (a), (b), and (c),except that the sealant construction of the packaging material for abattery is different from that of the packaging material shown in (a),(b), and (c);

[0046]FIG. 1B is a cross-sectional view showing an example of the layerconstruction of a laminate for an armor body for a battery;

[0047]FIG. 1C is a perspective view illustrating a pouch-type armor bodyfor a battery;

[0048]FIG. 1D is a perspective view illustrating an emboss-type armorbody for a battery;

[0049]FIG. 1E is a diagram illustrating molding in the case of an embosstype, wherein (a) is a perspective view, (b) an emboss molded main bodyfor an armor body, (c) a cross-sectional view taken on line X2-X2, and(d) an enlarged view of Y1 part;

[0050]FIG. 1F is a diagram illustrating a method for mounting a film fora lead in bonding between the packaging material for a battery and thelead;

[0051]FIG. 1G is a cross-sectional view illustrating the state ofshort-circuiting between a barrier layer and a lead in the case whereconventional packaging material for a battery and a film for a lead areused;

[0052]FIG. 1H is a diagram showing root cutting caused at the time ofhermetic sealing of the peripheral edge of an armor body using aconventional packaging material for a battery, wherein (a) is aperspective view of a battery, (b) a cross-sectional view taken on lineX-X, and (c) an enlarged view of Y1 part;

[0053]FIG. 2A is a diagram illustrating a packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing the layer construction of a packagingmaterial for a battery and the positional relationship among thepackaging material, a film for a lead, and a lead, (b) a cross-sectionalview illustrating the state of contact among the lead, the film for alead, and an armor body before heat sealing at the lead part, (c) atypical cross-sectional view of the lead part after heat sealing, and(d), (e), and (f) the same explanatory views as (a), (b), and (c),except that the sealant construction of the packaging material for abattery is different from that of the packaging material shown in (a),(b), and (c);

[0054]FIG. 2B is a cross-sectional view showing an example of the layerconstruction of a laminate for an armor body for a battery;

[0055]FIG. 2C is a perspective view illustrating a pouch-type armor bodyfor a battery;

[0056]FIG. 2D is a perspective view illustrating an emboss-type armorbody for a battery;

[0057]FIG. 2E is a diagram illustrating molding in the case of an embosstype, wherein (a) is a perspective view, (b) an emboss molded main bodyfor an armor body, (c) a cross-sectional view taken on line X2-X2, and(d) an enlarged view of Y1 part;

[0058]FIG. 2F is a diagram illustrating a method for mounting a film fora lead in bonding between the packaging material for a battery and thelead;

[0059]FIG. 2G is a cross-sectional view illustrating the state ofshort-circuiting between a barrier layer and a lead in the case whereconventional packaging material for a battery and a film for a lead areused;

[0060]FIG. 2H is a diagram showing root cutting caused at the time ofhermetic sealing of the peripheral edge of an armor body using aconventional packaging material for a battery, wherein (a) is aperspective view of a battery, (b) a cross-sectional view taken on lineX3--X3, and (c) an enlarged view of Y2 part;

[0061]FIG. 3A is a diagram illustrating a packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing an embodiment of the layer construction ofthe packaging material for a battery, and (b) a cross-sectional viewshowing another embodiment of the layer construction of the packagingmaterial for a battery;

[0062]FIG. 3B is a diagram illustrating the packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing the positional relationship between thepackaging material for a battery (layer construction of the packagingmaterial being shown) and a lead, (b) a cross-sectional viewillustrating the state of contact of the lead with the armor body at thelead part before heat sealing, (c) a typical cross-sectional view of thelead part after heat sealing, (d) a cross-sectional view showing thepositional relationship among the packaging material for a battery(layer construction of the packaging material being shown), a film forthe lead, and the lead, (e) a cross-sectional view illustrating thestate of contact among the lead, the film for the lead, and the armorbody before heat sealing, and (f) a typical cross-sectional view of thelead part after heat sealing;

[0063]FIG. 3C is a perspective view illustrating a pouch-type armor bodyfor a battery;

[0064]FIG. 3D is a perspective view illustrating an emboss-type armorbody for a battery;

[0065]FIG. 3E is a diagram illustrating molding in the case of an embosstype, wherein (a) is a perspective view, (b) an emboss molded main bodyfor an armor body, (c) a cross-sectional view taken on line X2-X2, and(d) an enlarged view of Y1 part;

[0066]FIG. 3F is a diagram illustrating a method for mounting a film fora lead in bonding between the packaging material for a battery and thelead;

[0067]FIG. 3G is a diagram illustrating root cutting in an adhesiveresin layer having a conventional composition, wherein (a) is across-sectional view of a packaging material for a battery and (b) anenlarged view of Y2 part;

[0068]FIG. 3H is a diagram showing root cutting caused at the time ofhermetic sealing of the peripheral edge of an armor body using aconventional packaging material for a battery, wherein (a) is aperspective view of a battery, (b) a cross-sectional view taken on lineX3-X3, and (c) an enlarged view of Y2 part;

[0069]FIG. 4A is an explanatory view of the packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing Example D of a laminate and (b) across-sectional view showing Example D of another laminate;

[0070]FIG. 4B is a diagram illustrating the construction of a sealantlayer, wherein (a) is a cross-sectional view of a sealant layer having asingle-layer structure, (b) a cross-sectional view of a sealant layerhaving a two-layer structure, and (c) a cross-sectional view of asealant layer having a three-layer structure;

[0071]FIG. 4C is a cross-sectional view of packaging materials for abattery according to the present invention which are different from oneanother in lamination method used for the formation thereof, wherein (a)is a diagram showing a packaging material formed by dry lamination, (b)a diagram showing a packaging material formed by hot lamination, (c) adiagram showing a packaging material formed by sandwich lamination, and(d) a diagram showing a packaging material formed by coextrusionlamination;

[0072]FIG. 4D is a perspective view illustrating a pouch-type armor bodyfor a battery;

[0073]FIG. 4E is a perspective view illustrating an emboss-type armorbody for a battery; and

[0074]FIG. 4F illustrates molding at the time of the formation of anemboss-type armor body, wherein (a) is a perspective view, (b) a diagramshowing an emboss molded main body of an armor body, (c) across-sectional view taken on line X2-X2, and (d) an enlarged view of Y1part.

DESCRIPTION OF REFERENCE CHARACTERS OF THE DRAWINGS

[0075] A. FIGS. 1A to 1H

[0076] S: short-circuit part between lead and barrier layer, H: heatsealing hot plate, C: root cutting part, t: resin pool, 1: battery, 2:battery body, 3: cell (accumulating part), 4: lead (electrode), 5: armorbody, 6: film for lead, 7: concave portion, 8: side wall part, 9: sealedpart, 10: laminate (packaging material for battery), 11: substratelayer, 12: aluminum (barrier layer), 13: dry laminate layer, 14: sealantlayer, 14 f: high-fluidity PP layer, 14 r: low-fluidity PP layer, 15:protective layer, 16: substrate-side dry laminate layer, 20: pressmolding part, 21: male mold, 22: female mold, and 23: cavity.

[0077] B. FIGS. 2A to 2H

[0078] S: short-circuit part between lead and barrier layer, H: heatsealing hot plate, C: root cutting part, t: resin pool, 1: battery, 2:battery body, 3: cell (accumulating part), 4: lead (electrode), 5: armorbody, 6: film for lead, 7: concave portion, 8: side wall part, 9: sealedpart, 10: laminate (packaging material for battery), 11: substratelayer, 12: aluminum (barrier layer), 13: adhesive resin layer, 13 h:baked layer of acid-modified polyolefin, 13 e: extruded layer ofacid-modified polyolefin, 14: sealant layer, 14 f: high-fluidity PPlayer, 14 r: low-fluidity PP layer, 15: protective layer, 16:substrate-side dry laminate layer, 20: press molding part, 21: malemold, 22: female mold, and 23: cavity.

[0079] C. FIGS. 3A to 3H

[0080] H: heat sealing bar, C: root cutting, 1: battery, 2: batterybody, 3: cell (accumulating part), 4: lead (electrode), 5: armor body,6: film for lead, 7: concave portion, 8: side wall part, 9: sealed part,10: laminate (packaging material for battery), 11: substrate layer, 12:aluminum (barrier layer), 13: adhesive resin layer, 14: sealant layer,Mx: heat fused layer, 15: conversion treated layer, 16: substrate-sidedry laminate layer, 20: press molding part, 21: male mold, 22: femalemold, and 23: cavity.

[0081] D. FIGS. 4A to 4F

[0082] H: heat sealing hot plate, 1: battery, 2: battery body, 3: cell(accumulating part), 4: lead (electrode), 5: armor body, 7: concaveportion, 8: side wall part, 9: sealed part, 10: laminate (packagingmaterial for battery), 11: substrate layer, 12: aluminum (barrierlayer), 13: adhesive layer, 13 d: dry laminate layer, 13 h: baked layerof acid-modified polyolefin, 13 es: extruded layer of acid-modifiedpolyolefin in the case of sandwich lamination, 13 ec: extruded layer ofacid-modified polyolefin in the case of coextrusion lamination, 14:sealant layer, S1: outer layer in sealant layer, S2: intermediate layerin sealant layer, S3: inner layer in sealant layer, 15: conversiontreated layer, 16: substrate-side dry laminate layer, 20: press moldingpart, 21: male mold, 22: female mold, and 23: cavity.

DETAILED DESCRIPTION OF THE INVENTION

[0083] A. First Aspect of the Invention

[0084] 1. Specific Embodiments

[0085] Specific embodiments of the first aspect of the present inventionare as follows. Specifically, the invention as defined in claim 1provides a packaging material for forming an armor body for a battery,said armor body being adapted for use in such a manner that a batterybody is inserted into the armor body and the peripheral edge of thearmor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, a barrier layer, a dry laminate layer, and a sealantlayer, characterized in that at least the sealant layer comprises alow-fluidity polypropylene layer having low susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing and ahigh-fluidity polypropylene layer having high susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing, and theinnermost layer is the high-fluidity polypropylene layer. The inventionas defined in claim 2 is characterized in that the barrier layer asdefined in claim 1 comprises at least a conversion treated layerprovided on its dry laminate layer side. The invention as defined inclaim 3 is characterized in that the sealant layer as defined in claim 1or 2 has a two-layer structure of the low-fluidity polypropylene layerand the high-fluidity polypropylene layer and the high-fluiditypolypropylene layer is the innermost layer. The invention as defined inclaim 4 is characterized in that the sealant layer as defined in claim 1or 2 has a three-layer structure of the high-fluidity polypropylenelayer, the low-fluidity polypropylene layer, and the high-fluiditypolypropylene layer. The invention as defined in claim 5 ischaracterized in that a film for a lead is interposed between thepackaging material for a battery as defined in any one of claims 1 to 4and a lead part in the battery body.

[0086] 2. Embodiments of the Invention

[0087] The present invention will be described in more detail withreference to the accompanying drawings and the like.

[0088]FIG. 1A is a diagram illustrating the packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing the layer construction of a packagingmaterial for a battery and the positional relationship between thepackaging material and a lead, (b) a cross-sectional view illustratingthe state of contact of the lead and an armor body before heat sealingat the lead part, (c) a typical cross-sectional view of the lead partafter heat sealing, and (d), (e), and (f) the same explanatory views as(a), (b), and (c), except that the sealant construction of the packagingmaterial for a battery is different from that of the packaging materialshown in (a), (b), and (c). FIG. 1B is a cross-sectional view showing anexample of the layer construction of a laminate for an armor body for abattery. FIG. 1C is a perspective view illustrating a pouch-type armorbody for a battery. FIG. 1D is a perspective view illustrating anemboss-type armor body for a battery. FIG. 1E is a diagram illustratingmolding in the case of an emboss type, wherein (a) is a perspectiveview, (b) an emboss molded main body for an armor body, (c) across-sectional view taken on line X2-X2, and (d) an enlarged view of Y1part. FIG. 1F is a diagram illustrating a method for mounting a film fora lead in bonding between the packaging material for a battery and thelead.

[0089] The lead for a battery is formed of an elongated sheet or rodmetal. The sheet lead has a thickness of 50 to 2,000 μm and a width ofabout 2.5 to 20 mm and is formed of aluminum (Al), copper (Cu) (copperplated with nickel (Ni)), nickel or the like.

[0090] A capability of maintaining the performance of the battery bodyfor a long period of time is required of the armor body for a battery,and the armor body for a battery comprises a substrate layer, a barrierlayer, a heat seal layer and the like stacked on top of one another byvarious lamination methods. In particular, when the heat seal layer inthe laminate constituting the armor body for a battery (hereinafterreferred to as “armor body”) comprises a polyolefin resin or the likeand, in this case, when an acid-modified polyolefin film is used in aportion where a lead exists, for example, as a film for a lead, inhousing the battery body in the armor body and hermetically sealing theassembly by sealing the peripheral edge, both the sealant layer in thearmor body and the film layer for a lead are melted by heat and pressurefor heat sealing and, further, upon the application of pressure, thebarrier layer in the armor body often comes into contact with the leadformed of a metal, resulting in short-circuiting S.

[0091] As shown in FIGS. 1H(a) to 1H(c), at the time of heat sealing ofthe peripheral edge of the armor body, microcracks often occur in thesealant layer around the inner edge of the sealed part (thesemicrocracks being hereinafter referred to as “root cutting C”). When theroot cutting occurs, the electrolysis solution comes into direct contactwith the barrier layer. This breaks insulation among the battery body,the metal constituting the lead, and the barrier layer and consequentlycreates a potential difference. The potential difference results in theformation of throughholes due to the corrosion of the barrier layer andthe formation of a reaction product of a metal ion as the electrolytecalled “dendrite.” These unfavorable phenomena shorten the service lifeof the battery.

[0092] The present inventors have made extensive and intensive studieson the prevention of the short-circuit S and, as a result, have foundthat the above problem can be solved by adopting such a constructionthat the packaging material for forming the armor body, for a battery,adapted for use in such a manner that a battery body is inserted intothe armor body and the peripheral edge of the armor body is then heatsealed for hermetic sealing, is a laminate comprising at least asubstrate layer, an adhesive layer, a barrier layer, a dry laminatelayer, and a sealant layer, at least the sealant layer has a multilayerstructure of a low-fluidity polypropylene layer having lowsusceptibility to collapse upon exposure to heat and pressure at thetime of heat sealing (hereinafter referred to as “low-fluidity PP layer”or “low-fluidity PP”) and a high-fluidity polypropylene layer havinghigh susceptibility to collapse upon exposure to heat and pressure atthe time of heat sealing (hereinafter referred to as “high-fluidity PPlayer” or “high-fluidity PP”), and the innermost layer is thehigh-fluidity PP layer. This has led to the completion of the presentinvention.

[0093] The multilayered sealant in a packaging material for a batteryaccording to the present invention exhibits low fluidity also in such astate that, in hermetically sealing the armor body by heat sealing, thelow-fluidity PP layer has been brought to a melted resin upon theapplication of heat and pressure at the time of heat sealing under heatsealing conditions suitable for hermetic sealing of the packagingmaterial for a battery. This allows an insulating film to exist betweenthe barrier layer and the lead, and root cutting around the sealed partcan be advantageously prevented. On the other hand, upon melting, thehigh-fluidity PP layer becomes a low-viscosity state which has theeffect of hermetically sealing the portion different in level. Further,the seal is pressed and collapsed to reduce the thickness of the sealand to reduce the sectional area of the sealed part. This canadvantageously reduce moisture permeation through the cross section.

[0094] The fluidity of the low-fluidity PP and the fluidity of thehigh-fluidity PP can be distinguished from each other by melt indexvalues (hereinafter referred to as “MI”) as measured according to JIS K7210. In the present invention, the low-fluidity PP preferably has an MIvalue of 0.5 to 3.0 g/10 min, and the high-fluidity PP preferably has anMI value of 5.0 to 30 g/10 min.

[0095] As shown, for example, in FIG. 1B(a), the packaging material fora battery according to the present invention is a laminate comprising atleast a substrate layer 11, an adhesive layer 16, aluminum 12, aprotective layer 15, a dry laminate adhesive layer 13 d, and amultilayered sealant layer 14, wherein the multilayered sealant has atwo-layer structure of a low-fluidity PP layer 14 r and a high-fluidityPP layer 14 f.

[0096] Further, for example, as shown in FIG. 1B(a), the packagingmaterial may be a laminate comprising at least a substrate layer 11, anadhesive layer 16, aluminum 12, a protective layer 15, a dry laminateadhesive layer 13 d, and a multilayered sealant layer 14, wherein themultilayered sealant has a three-layer structure of a high-fluidity PPlayer 14 f (1), a low-fluidity PP layer 14 r, and a high-fluidity PPlayer 14 f (2).

[0097] The layer thickness ratio between the high-fluidity polypropylenelayer and low-fluidity polypropylene layer in the sealant layer in thepackaging material for a battery according to the present invention ispreferably such that the thickness of the low-fluidity PP is 1.5 timesor more that of the high-fluidity PP. Specifically, low-fluidity PPhigh-fluidity PP=95:5 to 60:40 is suitable.

[0098] When the sealant layer has a three-layer structure, inhigh-fluidity PP (1)/low-fluidity PP/high-fluidity PP (2), the thicknessof the low-fluidity PP is preferably 1.5 times or more the totalthickness of the high-fluidity PP (1) and the high-fluidity PP (2).

[0099] Specifically, when the thickness of the low-fluidity PP is lessthan 1.5 times the thickness of the high-fluidity PP (the totalthickness of the outer layer and the inner layer in the case of thethree-layer structure), the effect of rendering the low-fluidity PP lesssusceptible to collapse upon heat sealing is less likely to appear.Therefore, short-circuiting between the barrier layer and the lead islikely to occur, and, thus, root cutting cannot be prevented. The totalthickness of the sealant layer is suitably 20 μm to 200 μm.

[0100] Polypropylene used in the sealant layer according to the presentinvention may be homo-type polypropylene, random-type polypropylene, orblock-type polypropylene.

[0101] Since polypropylenes constituting the sealant layer in thepackaging material for a battery according to the present invention donot have any adhesion to a metal, a film for a lead having heat sealingproperties on both the sealant layer and the lead at the time ofhermetic sealing should be interposed between the lead part in thebattery and the armor body. For example, as shown in FIGS. 1F(a) and1F(b), a film 6 for a lead is placed on the upper side and the lowerside of the hermetic sealing part of the lead 4 in the battery body 2(in fact, the film being fixed by temporary sealing on the upper sideand the lower side of the hermetic sealing part), and the battery body 2is inserted into the armor body 5, followed by heat sealing in such astate that the lead part is sandwiched, whereby the assembly ishermetically sealed. An example of a method for placing the film 6 for alead on the lead 4 is to wind a film 6 for a lead around the lead 4 atits predetermined position, as shown in FIG. 1F(d) or FIG. 1F(e).

[0102] Specific examples of materials for films for a lead includeacid-modified polypropylene (unsaturated carboxylic acid-grafted randompropylene), metal-crosslinked polyethylene, a copolymer of ethylene withan acrylic acid or methacrylic acid derivative, and a copolymer ofethylene with vinyl acetate. These materials may be used solely, as ablend of two or more, or in other forms.

[0103] The layer thickness of the film 6 for a lead may be one-third ormore of the thickness of the lead 4 used. For example, when thethickness of the lead 4 is 100 μm, the total thickness of the film 6 fora lead may be about 30 μm or more.

[0104] When an armor body is formed using the packaging material for abattery according to the present invention and a battery body isinserted into the armor body followed by heat sealing of the peripheraledge of the assembly for hermetic sealing, the seal state in the leadpart is such that, as shown in FIG. 1A(c) or FIG. 1A(f), thelow-fluidity PP layer 14 r stays in a film form and consequently,short-circuiting between the barrier layer 12 and the lead 4 and rootcutting, which are problems to be solved by the present invention, canbe avoided.

[0105] The packaging material for a battery is used for the formation ofan armor body for packaging a battery body, and types of the packagingmaterial may be divided according to the type of the armor body into apouch type as shown in FIG. 1C and an emboss type as shown in FIG.1D(a), FIG. 1D(b), or FIG. 1D(c). The pouch type may be a bag type suchas a three sided seal type, a four sided seal type, or a pillow type.FIG. 1C shows a pillow type as an example of the type of the armor body.

[0106] In the emboss type, as shown in FIG. 1D(a), a concave portion maybe formed on one side of the armor body. Alternatively, a constructionmay be adopted wherein, as shown in FIG. 1D(b), a concave portion isformed on both sides of the armor body, a battery body is housed in thearmor body, and the four peripheral sides of the armor body are heatsealed to hermetically seal the assembly. Further, a construction mayalso be adopted wherein, as shown in FIG. 1D(c), a concave portion isformed on both sides of the armor body with a folded portion sandwiched,a battery is housed in the armor body, and the three sides of the armorbody are heat sealed. When the packaging material for a battery is of anemboss type, as shown in FIGS. 1E(a) to 1E(d), the stacked packagingmaterial 10 is subjected to press molding to form a concave portion 7.

[0107] Next, each layer constituting the packaging material for abattery according to the present invention will be described. Thesubstrate layer 11 in the armor body is formed of an oriented polyesteror a nylon film. Polyester resins usable herein include polyethyleneterephthalate, polybutylene terephthalate, polyethylene naphthalate,polybutylene naphthalate, interpolyester, and polycarbonate. Nylonsusable herein include polyamide resins, that is, nylon 6, nylon 6, 6, acopolymer of nylon 6 with nylon 6, 6, nylon 6, 10, andpoly-m-xylyleneadipamide (MXD 6).

[0108] When the substrate layer 11 is used as a battery, the substratelayer 11 is a site which comes into direct contact with the hardware.Therefore, basically, the substrate layer 11 is preferably a resin layerhaving insulating properties. When the presence of pinholes in the filmper se, the occurrence of pinholes at the time of fabrication and thelike are taken into consideration, the substrate layer should have athickness of not less than 6 μm, preferably 12 to 30 μm.

[0109] In order to improve anti-pinhole properties and insulatingproperties of the armor body for a battery, the substrate layer 11 maybe in the form of a laminate. When the substrate layer is in the form ofa laminate, the substrate layer includes at least one unit of two ormore resin layers and, in this case, the thickness of each layer is notless than 6 μm, preferably 12 to 30 μm. Examples of the substrate layerhaving a multilayer structure include the following layerconstructions 1) to 8).

[0110] 1) Oriented polyethylene terephthalate/oriented nylon

[0111] 2) Oriented nylon/oriented polyethylene terephthalate. Further,from the viewpoint of machinability (stable carriage in a packagingmachine or a processing machine), surface protective properties (heatresistance and electrolyte resistance), a reduction in frictionalresistance between the mold and the substrate layer at the time ofembossing to form an emboss-type armor body for a battery byfabrication, or protection of the substrate layer upon the deposition ofan electrolysis solution, preferably, the substrate layer has amultilayer structure, and a fluororesin layer, an acrylic resin layer, asilicone resin layer, a polyester resin layer, a slip agent such as anoleic acid amide, an erucic acid amide, or a bisoleic acid amide, aresin layer formed of a blend of two or more of the above materials orthe like is provided on the surface of the substrate layer. Examples ofthis type of substrate layer include,

[0112] 3) fluororesin/oriented polyethylene terephthalate (thefluororesin layer is constituted by a fluororesin film or is formed byliquid coating and then drying),

[0113] 4) silicone resin/oriented polyethylene terephthalate (thesilicone resin layer is constituted by a silicone resin film or isformed by liquid coating and then drying),

[0114] 5) fluororesin/oriented polyethylene terephthalate/orientednylon,

[0115] 6) silicone resin/oriented polyethylene terephthalate/orientednylon,

[0116] 7) acrylic resin/oriented nylon (the acrylic resin layer isconstituted by an acrylic resin film or is formed by liquid coating andthen drying for curing), and

[0117] 8) acrylic resin+polysiloxane-grafted acrylic resin/orientednylon (the acrylic resin layer is constituted by an acrylic resin filmor is formed by liquid coating and then drying for curing).

[0118] The barrier layer 12 is a layer for preventing the entry ofparticularly water vapor in the battery from the exterior. From theviewpoints of pinholes in the barrier layer per se and stabilization offabricability (pouching or emboss moldability) and of impartinganti-pinhole properties, not less than 15 μm-thick aluminum, nickel orother metal, or a film with an inorganic compound, for example, siliconoxide or alumina, vapor deposited thereon may be mentioned as thebarrier layer. Preferably, however, the barrier layer comprises 20 to80-μm thick aluminum as a base and a protective layer, which will bedescribed later, provided on the aluminum.

[0119] When a further reduction in occurrence of pinholes and theformation of an emboss-type armor body for a battery are contemplated,studies conducted by the present inventors have revealed that, in orderto prevent cracking and the like at the time of emboss molding, when thebarrier layer is formed of aluminum having an iron content of 0.3 to9.0% by weight, preferably 0.7 to 2.0% by weight, as compared withiron-free aluminum, the iron-containing aluminum has better ductilityand the occurrence of pinholes of the laminate by folding can be reducedand, at the same time, the formation of the side wall at the time ofmolding of the emboss-type armor body is easier. When the iron contentis less than 0.3% by weight, for example, the effect of preventing theoccurrence of pinholes and the effect of improving emboss moldabilitycannot be attained. On the other hand, when the iron content of thealuminum exceeds 9.0% by weight, the flexibility as the aluminum ishindered and the suitability of the laminate for bag making isdeteriorated.

[0120] For aluminum produced by cold rolling, the flexibility, thenerve, and the hardness vary depending upon conditions for annealingtreatment. For aluminum used in the present invention, somewhat or fullyannealed aluminum, which is relatively soft, is preferred rather than ahardening treated product not subjected to annealing. The flexibility,nerve, and hardness of aluminum, that is, conditions for annealing, maybe properly selected according to suitability for fabrication (pouchingor emboss molding). For example, in order to prevent the occurrence ofwrinkles and pinholes at the time of emboss molding, the use of softaluminum, which has been annealed depending upon the degree of molding,is preferred.

[0121] The present inventors have found that, for example, whenconversion treatment is carried out to form a protective layer on thefront and back sides of aluminum as the barrier layer 12 in thepackaging material for a battery, a laminate, which is satisfactory asthe packaging material, can be provided. Specifically, the conversiontreatment refers to the formation of an acid-resistant film of a salt ofphosphoric acid, a salt of chromic acid, a fluoride, a triazinethiolcompound or the like. Phosphoric acid chromate treatment using athree-component system of a phenolic resin, a chromium(III) fluoridecompound, and phosphoric acid among the above acid-resistant filmforming materials can provide good results. Further, a conversiontreating agent comprising a resin component containing at least aphenolic resin and, added thereto, a metal, such as molybdenum,titanium, or zirconium, or a metal salt can provide good results. Theformation of the acid-resistant film can advantageously preventdelamination between the aluminum and the substrate layer at the time ofemboss molding, can prevent dissolution and corrosion of the surface ofaluminum, particularly dissolution and corrosion of aluminum oxidepresent on the surface of the aluminum, by hydrogen fluoride produced asa result of a reaction of an electrolyte in the battery with water, canimprove the adhesion (wettability) of the surface of aluminum, canprevent delamination between the substrate layer 11 and the aluminum 12at the time of emboss molding and heat sealing, and can preventdelamination on the inner side of the aluminum by hydrogen fluorideproduced as a result of a reaction of the electrolyte with water.

[0122] The present inventors have carried out conversion treatment ofthe surface of the aluminum using various materials and have madestudies on the effect of the conversion treatment. As a result, it wasfound that phosphoric acid chromate treatment using a three-componentsystem of a phenolic resin, a chromium(III) fluoride compound, andphosphoric acid among the above acid-resistant film forming materialscan provide good results.

[0123] Further, a conversion treating agent comprising a resin componentcontaining at least a phenolic resin and, added thereto, a metal, suchas molybdenum, titanium, or zirconium, or a metal salt can provide goodresults.

[0124] When the armor body is of a pouch type, the conversion treatmentmay be carried out on one side (only heat seal layer side) of thealuminum or both sides (substrate layer side and heat seal layer side).On the other hand, when the armor body of the battery is of an embosstype, conversion treatment of both sides of the aluminum can preventdelamination between the aluminum and the substrate layer at the time ofemboss molding.

[0125] As described above, the sealant layer in the packaging materialfor a battery according to the present invention has a multilayerstructure of a combination of low-fluidity PP with high-fluidity PP, andthe innermost layer is the high-fluidity PP. The total thickness of thesealant layer is preferably 20 to 200 μm.

[0126] Bonding between the protective layer provided on the barrierlayer and the sealant layer in the lamination of the packaging materialfor a battery according to the present invention is preferably carriedout by dry lamination, for example, from the viewpoint of preventingdelamination by hydrofluoric acid or the like evolved as a result of areaction of the electrolysis solution in a lithium ion battery or thelike with water.

[0127] In the packaging material for a battery according to the presentinvention, each of the layers constituting the laminate for armor bodyformation may be properly subjected to surface activation treatment,such as corona treatment, blast treatment, oxidation treatment, or ozonetreatment, from the viewpoints of improving or stabilizing film formingproperties, lamination, and suitability for fabrication of the finalproduct (pouching or emboss molding).

[0128] B. Second Aspect of the Invention

[0129] 1. Specific Embodiments

[0130] Specific embodiments of the second aspect of the presentinvention are as follows. Specifically, the invention as defined inclaim 6 provides a packaging material for forming an armor body for abattery, said armor body being adapted for use in such a manner that abattery body is inserted into the armor body and the peripheral edge ofthe armor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, a barrier layer, an adhesive resin layer, and a sealantlayer, characterized in that at least the sealant layer comprises alow-fluidity polypropylene layer having low susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing and ahigh-fluidity polypropylene layer having high susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing, and theinnermost layer is the high-fluidity polypropylene layer.

[0131] The invention as defined in claim 7 is characterized in that thebarrier layer as defined in claim 6 comprises at least a conversiontreated layer provided on its adhesive resin layer side.

[0132] The invention as defined in claim 8 is characterized in that thesealant layer as defined in claim 6 or 7 has a two-layer structure ofthe low-fluidity polypropylene layer and the high-fluidity polypropylenelayer and the high-fluidity polypropylene layer is the innermost layer.The invention as defined in claim 9 is characterized in that the sealantlayer as defined in claim 6 or 7 has a three-layer structure of thehigh-fluidity polypropylene layer, the low-fluidity polypropylene layer,and the high-fluidity polypropylene layer. The invention as defined inclaim 10 is characterized in that the adhesive resin layer as defined inany one of claims 6 to 9 is a baked layer of an emulsion of anacid-modified polyolefin, and the sealant layer has been adhered to thebaked layer by heat lamination. The invention as defined in claim 11 ischaracterized in that the adhesive resin layer as defined in any one ofclaims 6 to 9 is formed of acid-modified polypropylene and the sealantlayer has been previously formed and has been stacked onto the adhesiveresin layer by sandwich lamination. The invention as defined in claim 12is characterized in that the adhesive resin layer as defined in any oneof claims 6 to 9 is formed of acid-modified polypropylene and thesealant layer has been stacked onto the adhesive resin layer bycoextrusion lamination. The invention as defined in claim 13 ischaracterized in that an adhesive film is interposed between thepackaging material for a battery as defined in any one of claims 6 to 12and a lead part in the battery body.

[0133] 2. Embodiments of the Invention

[0134] The packaging material for a battery according to the presentinvention comprises at least a substrate layer, an adhesive layer, abarrier layer, an adhesive resin layer, and a sealant layer. In thispackaging material, a combination of a layer having high susceptibilityto collapse upon exposure to heat and pressure at the time of heatsealing and a layer having low susceptibility to collapse upon exposureto heat and pressure at the time of heat sealing is adopted forconstituting the sealant layer. This combination can prevent rootcutting of the sealant layer and can realize a seal free fromshort-circuiting between the barrier layer and the lead. The presentinvention will be described in more detail with reference to theaccompanying drawings and the like.

[0135]FIG. 2A is a diagram illustrating the packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing the layer construction of a packagingmaterial for a battery and the positional relationships of the packagingmaterial and a lead, (b) a cross-sectional view illustrating the stateof contact of the lead and an armor body before heat sealing at the leadpart, (c) a typical cross-sectional view of the lead part after heatsealing, and (d), (e), and (f) are the same explanatory views as (a),(b), and (c), except that the sealant construction of the packagingmaterial for a battery is different from that of the packaging materialshown in (a), (b), and (c). FIG. 2B is a cross-sectional view showing anexample of the layer construction of a laminate for an armor body for abattery. FIG. 2C is a perspective view illustrating a pouch-type armorbody for a battery. FIG. 2D is a perspective view illustrating anemboss-type armor body for a battery. FIG. 2E is a diagram illustratingmolding in the case of an emboss type, wherein (a) is a perspectiveview, (b) an emboss molded main body for an armor body, (c) across-sectional view taken on line X2-X2, and (d) an enlarged view of Y1part. FIG. 2F is a diagram illustrating a method for mounting a film fora lead in bonding between the packaging material for a battery and thelead.

[0136] The lead for a battery is formed of an elongated sheet or rodmetal. The sheet lead has a thickness of 50 to 2,000 μm and a width ofabout 2.5 to 20 mm and is formed of aluminum (Al), copper (Cu) (copperplated with nickel (Ni)), nickel or the like.

[0137] The capability of maintaining the performance of the battery bodyfor a long period of time is required of the armor body for a battery,and the armor body for a battery comprises a substrate layer, a barrierlayer, a heat seal layer and the like stacked on top of one another byvarious lamination methods. In particular, when the heat seal layer inthe laminate constituting the armor body for a battery (hereinafterreferred to as “armor body”) comprises a polyolefin resin or the likeand, in this case, when an acid-modified polyolefin is used in a portionwhere a lead exists, for example, as a film for a lead, in housing thebattery body in the armor body and hermetically sealing the assembly bysealing the peripheral edge, both the heat seal layer in the armor bodyand the film layer for a lead are melted by heat and pressure for heatsealing and, further, upon the application of pressure, the barrierlayer in the armor body often comes into contact with the lead formed ofa metal, resulting in short-circuiting S.

[0138] As shown in FIGS. 2H(a) to 2H(c), at the time of heat sealing ofthe peripheral edge of the armor body, microcracks often occur in thesealant layer around the inner edge of the sealed part (thesemicrocracks being hereinafter referred to as “root cutting C”). When theroot cutting occurs, the electrolysis solution comes into direct contactwith the barrier layer. This breaks insulation among the battery body,the metal constituting the lead, and the barrier layer and consequentlycreates a potential difference. The potential difference results in theformation of throughholes due to the corrosion of the barrier layer andthe formation of a reaction product of a metal ion as the electrolytecalled “dendrite.” These unfavorable phenomena shorten the service lifeof the battery.

[0139] The present inventors have made extensive and intensive studieson the prevention of the short-circuit S and, as a result, have foundthat the above problem can be solved by adopting such a constructionthat the packaging material for forming the armor body, for a battery,adapted for use in such a manner that a battery body is inserted intothe armor body and the peripheral edge of the armor body is then heatsealed for hermetic sealing, is a laminate comprising at least asubstrate layer, an adhesive layer, a barrier layer, an adhesive resinlayer, and a sealant layer, at least the sealant layer has a multilayerstructure of a low-fluidity polypropylene layer having lowsusceptibility to collapse upon exposure to heat and pressure at thetime of heat sealing (hereinafter referred to as “low-fluidity PP layer”or “low-fluidity PP”) and a high-fluidity polypropylene layer havinghigh susceptibility to collapse upon exposure to heat and pressure atthe time of heat sealing (hereinafter referred to as “high-fluidity PPlayer” or “high-fluidity PP”), and the innermost layer is thehigh-fluidity PP layer. This has led to the completion of the presentinvention.

[0140] The multilayered sealant in a packaging material for a batteryaccording to the present invention exhibits low fluidity also in such astate that, in hermetically sealing the armor body by heat sealing, thelow-fluidity PP layer has been brought to a melted resin upon theapplication of heat and pressure at the time of heat sealing under heatsealing conditions suitable for hermetic sealing of the packagingmaterial for a battery. This allows an insulating film to exist betweenthe barrier layer and the lead, and root cutting around the sealed partcan be advantageously prevented. On the other hand, upon melting, thehigh-fluidity PP layer becomes a low-viscosity state which has theeffect of hermetically sealing the portion different in level. Further,upon heat sealing, the thickness of the layer is reduced due to pressingand collapsing to reduce the sectional area of the sealed part. This canadvantageously reduce moisture permeation through the cross section.

[0141] The fluidity of the low-fluidity PP and the fluidity of thehigh-fluidity PP can be distinguished from each other by melt indexvalues (hereinafter referred to as “MI”) as measured according to JIS K7210.

[0142] In the present invention, the low-fluidity PP preferably has anMI value of 0.5 to 3.0 g/10 min, and the high-fluidity PP preferably hasan MI value of 5.0 to 30 g/10 min.

[0143] As shown, for example, in FIG. 2B(a) or FIG. 2B(b), the packagingmaterial for a battery according to the present invention is a laminatecomprising at least a substrate layer 11, an adhesive layer 16, aluminum12, a protective layer 15, an adhesive resin layer 13 d, and amultilayered sealant layer 14, wherein the multilayered sealant has atwo-layer structure of a low-fluidity PP layer 14 r and a high-fluidityPP layer 14 f. Further, for example, as shown in FIG. 2B(c) or FIG.2B(d), the packaging material may be a laminate comprising at least asubstrate layer 11, an adhesive layer 16, aluminum 12, a protectivelayer 15, an adhesive resin layer 13 d, and a multilayered sealant layer14, wherein the multilayered sealant has a three-layer structure of ahigh-fluidity PP layer 14 f (1), a low-fluidity PP layer 14 r, and ahigh-fluidity PP layer 14 f (2).

[0144] The layer thickness ratio between the high-fluidity polypropylenelayer and low-fluidity polypropylene layer in the sealant layer in thepackaging material for a battery according to the present invention ispreferably such that the thickness of the low-fluidity PP is 1.5 timesor more that of the high-fluidity PP. Specifically, low-fluidity PPhigh-fluidity PP=95:5 to 60:40 is suitable.

[0145] When the sealant layer has a three-layer structure, inhigh-fluidity PP (1)/low-fluidity PP/high-fluidity PP (2), the thicknessof the low-fluidity PP is preferably 1.5 times or more the totalthickness of the high-fluidity PP (1) and the high-fluidity PP (2).

[0146] Specifically, when the thickness of the low-fluidity PP is lessthan 1.5 times the thickness of the high-fluidity PP (the totalthickness of the outer layer and the inner layer in the case of thethree-layer structure), the effect of rendering the low-fluidity PP lesssusceptible to collapse upon heat sealing is less likely to appear.Therefore, short-circuiting between the barrier layer and the lead islikely to occur, and, thus, root cutting cannot be prevented.

[0147] The total thickness of the sealant layer is suitably 20 μm to 200μm.

[0148] Polypropylene used in the sealant layer according to the presentinvention may be homo-type polypropylene, random-type polypropylene, orblock-type polypropylene.

[0149] Since polypropylenes constituting the sealant layer in thepackaging material for a battery according to the present invention donot have any adhesion to a metal, a film for a lead having heat sealingproperties on both the sealant layer and the lead at the time ofhermetic sealing should be interposed between the lead part in thebattery and the armor body. For example, as shown in FIGS. 2F(a) and2F(b), a film 6 for a lead is placed on the upper side and the lowerside of the hermetic sealing part of the lead 4 in the battery body 2(in fact, the film being fixed by temporary sealing on the upper sideand the lower side of the hermetic sealing part), and the battery body 2is inserted into the armor body 5, followed by heat sealing in such astate that the lead 4 is sandwiched, whereby the assembly ishermetically sealed. An example of a method for placing the film 6 for alead on the lead 4 is to wind a film 6 for a lead around the lead 4 atits predetermined position, as shown in FIG. 2F(d) or FIG. 2F(e).

[0150] Specific examples of materials for the film 6 for a lead includeacid-modified polypropylene (unsaturated carboxylic acid-grafted randompropylene), metal-crosslinked polyethylene, a copolymer of ethylene withan acrylic acid or methacrylic acid derivative, and a copolymer ofethylene with vinyl acetate. These materials may be used solely, as ablend of two or more, or in other forms.

[0151] The layer thickness of the film 6 for a lead may be one-third ormore of the thickness of the lead 4 used. For example, when thethickness of the lead is 100 μm, the total thickness of the film 6 for alead may be about 30 μm or more.

[0152] When an armor body is formed using the packaging material for abattery according to the present invention and a battery body isinserted into the armor body followed by heat sealing of the peripheraledge of the assembly for hermetic sealing, the seal state in the leadpart is such that, as shown in FIG. 2B-A(c) or FIG. 2B-A(f), thelow-fluidity PP layer 14 r stays in a film form between the barrierlayer and the lead and consequently can avoid short-circuiting and rootcutting which are problems to be solved by the present invention.

[0153] The packaging material for a battery is used for the formation ofan armor body for packaging a battery body. The armor body may be of apouch type as shown in FIG. 2C or an emboss type as shown in FIG. 2D(a), FIG. 2D(b), or FIG. 2D(c). The pouch type may be a bag type such asa three sided seal type, a four sided seal type, or a pillow type. FIG.2C shows a pillow type as an example of the type of the armor body.

[0154] In the emboss type, as shown in FIG. 2D(a), a concave portion maybe formed on one side of the armor body. Alternatively, a constructionmay be adopted wherein, as shown in FIG. 2D(b), a concave portion isformed on both sides of the armor body, a battery body is housed in thearmor body, and the four peripheral sides of the armor body are heatsealed to hermetically seal the assembly. Further, a construction mayalso be adopted wherein, as shown in FIG. 2D(c), a concave portion isformed on both sides of the armor body with a folded portion sandwiched,a battery is housed in the armor body, and the three sides of the armorbody are heat sealed.

[0155] When the packaging material for a battery is of an emboss type,as shown in FIGS. 2E(a) to 2E(d), the stacked packaging material 10 issubjected to press molding to form a concave portion 7.

[0156] Next, each layer constituting the packaging material for abattery according to the present invention will be described.

[0157] The substrate layer 11 in the armor body is formed of an orientedpolyester or a nylon film. Polyester resins usable herein includepolyethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate, polybutylene naphthalate, interpolyester, andpolycarbonate. Nylons usable herein include polyamide resins, that is,nylon 6, nylon 6, 6, a copolymer of nylon 6 with nylon 6, 6, nylon 6,10, and poly-m-xylyleneadipamide (MXD 6).

[0158] When the substrate layer 11 is used as a battery, the substratelayer 11 is a site which comes into direct contact with the hardware.Therefore, basically, the substrate layer 11 is preferably a resin layerhaving insulating properties. When the presence of pinholes in the filmper se, the occurrence of pinholes at the time of fabrication and thelike are taken into consideration, the substrate layer should have athickness of not less than 6 μm, preferably 12 to 30 μm.

[0159] In order to improve anti-pinhole properties and insulatingproperties of the armor body for a battery, the substrate layer 11 maybe in the form of a laminate.

[0160] When the substrate layer is in the form of a laminate, thesubstrate layer includes at least one unit of two or more resin layersand, in this case, the thickness of each layer is not less than 6 μm,preferably 12 to 30 μm. Examples of the substrate layer having amultilayer structure include the following layer constructions 1) to 8).

[0161] 1) Oriented polyethylene terephthalate/oriented nylon, and

[0162] 2) Oriented nylon/oriented polyethylene terephthalate.

[0163] Further, from the viewpoint of machinability (stable carriage ina packaging machine or a processing machine) of the packaging material,surface protective properties (heat resistance and electrolyteresistance), a reduction in frictional resistance between the mold andthe substrate layer at the time of embossing to form an emboss-typearmor body for a battery by fabrication, or protection of the substratelayer upon the deposition of an electrolysis solution, preferably, thesubstrate layer has a multilayer structure, and a fluororesin layer, anacrylic resin layer, a silicone resin layer, a polyester resin layer, aslip agent such as an oleic acid amide, an erucic acid amide, or abisoleic acid amide, a resin layer formed of a blend of two or more ofthe above materials or the like is provided on the surface of thesubstrate layer. Examples of this type of substrate layer include

[0164] 3) fluororesin/oriented polyethylene terephthalate (thefluororesin layer is constituted by a fluororesin film or is formed byliquid coating and then drying),

[0165] 4) silicone resin/oriented polyethylene terephthalate (thesilicone resin layer is constituted by a silicone resin film or isformed by liquid coating and then drying),

[0166] 5) fluororesin/oriented polyethylene terephthalate/orientednylon,

[0167] 6) silicone resin/oriented polyethylene terephthalate/orientednylon,

[0168] 7) acrylic resin/oriented nylon (the acrylic resin layer isconstituted by an acrylic resin film or is formed by liquid coating andthen drying for curing), and

[0169] 8) acrylic resin+polysiloxane-grafted acrylic resin/orientednylon (the acrylic resin layer is constituted by an acrylic resin filmor is formed by liquid coating and then drying for curing).

[0170] The barrier layer 12 is a layer for preventing the entry ofparticularly water vapor in the battery from the exterior. From theviewpoints of pinholes in the barrier layer per se and stabilization offabrication or molding (pouching or emboss molding) and of impartinganti-pinhole properties, not less than 15 μm-thick aluminum, nickel orother metal, or a film with an inorganic compound, for example, siliconoxide or alumina, vapor deposited thereon may be mentioned as thebarrier layer. Preferably, however, the barrier layer is 20 to 80-μmthick aluminum.

[0171] When a further reduction in occurrence of pinholes and theformation of an emboss-type armor body for a battery are contemplated,studies conducted by the present inventors have revealed that, in orderto prevent cracking and the like at the time of emboss molding, when thebarrier layer is formed of aluminum having an iron content of 0.3 to9.0% by weight, preferably 0.7 to 2.0% by weight, as compared withiron-free aluminum, the iron-containing aluminum has better ductilityand the occurrence of pinholes of the laminate by folding can be reducedand, at the same time, the formation of the side wall at the time ofmolding of the emboss-type armor body is easier. When the iron contentis less than 0.3% by weight, for example, the effect of preventing theoccurrence of pinholes and the effect of improving emboss moldabilitycannot be attained. On the other hand, when the iron content of thealuminum exceeds 9.0% by weight, the flexibility as the aluminum ishindered and the suitability of the laminate for bag making isdeteriorated.

[0172] For aluminum produced by cold rolling, the flexibility, thenerve, and the hardness vary depending upon conditions for annealingtreatment. For aluminum used in the present invention, somewhat or fullyannealed aluminum, which is relatively soft, is preferred rather than ahardening treated product not subjected to annealing.

[0173] The flexibility, nerve, and hardness of aluminum, that is,conditions for annealing, may be properly selected according tosuitability for fabrication or molding (pouching or emboss molding). Forexample, in order to prevent the occurrence of wrinkles and pinholes atthe time of emboss molding, the use of soft aluminum, which has beenannealed depending upon the degree of molding, is preferred.

[0174] The present inventors have found that, for example, whenconversion treatment is carried out to form a protective layer on thefront and back sides of aluminum as the barrier layer 12 in thepackaging material for a battery, a laminate, which is satisfactory asthe packaging material, can be provided. Specifically, the conversiontreatment refers to the formation of an acid-resistant film of a salt ofphosphoric acid, a salt of chromic acid, a fluoride, a triazinethiolcompound or the like. Phosphoric acid chromate treatment using athree-component system of a phenolic resin, a chromium(III) fluoridecompound, and phosphoric acid among the above acid-resistant filmforming materials can provide good results. Further, a conversiontreating agent comprising a resin component containing at least aphenolic resin and, added thereto, a metal, such as molybdenum,titanium, or zirconium, or a metal salt can provide good results. Theformation of the acid-resistant film can prevent delamination betweenthe aluminum and the substrate layer at the time of emboss molding, canprevent dissolution and corrosion of the surface of aluminum,particularly dissolution and corrosion of aluminum oxide present on thesurface of the aluminum, by hydrogen fluoride produced as a result of areaction of an electrolyte in the battery with water, can improve theadhesion (wettability) of the surface of aluminum, can preventdelamination between the substrate layer 11 and the aluminum 12 at thetime of emboss molding and heat sealing, and can prevent delamination onthe inner side of the aluminum by hydrogen fluoride produced as a resultof a reaction of the electrolyte with water.

[0175] The present inventors have carried out conversion treatment ofthe surface of the aluminum using various materials and have madestudies on the effect of the conversion treatment. As a result, it wasfound that phosphoric acid chromate treatment using a three-componentsystem of a phenolic resin, a chromium(III) fluoride compound, andphosphoric acid among the above acid-resistant film forming materialscan provide good results.

[0176] Further, a conversion treating agent comprising a resin componentcontaining at least a phenolic resin and, added thereto, a metal, suchas molybdenum, titanium, or zirconium, or a metal salt can provide goodresults.

[0177] When the armor body is of a pouch type, the conversion treatmentmay be carried out on one side (only heat seal layer side) of thealuminum or both sides (substrate layer side and heat seal layer side).On the other hand, when the armor body of the battery is of an embosstype, conversion treatment of both sides of the aluminum can preventdelamination between the aluminum and the substrate layer at the time ofemboss molding.

[0178] As described above, the sealant layer in the packaging materialfor a battery according to the present invention has a multilayerstructure of a combination of low-fluidity PP with high-fluidity PP, andthe innermost layer is the high-fluidity PP. The total thickness of thesealant layer is preferably 20 to 200 μm.

[0179] Regarding bonding between the conversion treated layer providedon the barrier layer and the sealant layer in the lamination of thepackaging material for a battery according to the present invention, thefollowing lamination and bonding stabilization treatment are preferablycarried out, for example, from the viewpoint of preventing delaminationby hydrofluoric acid or the like evolved as a result of a reaction ofthe electrolysis solution in a lithium ion battery or the like withwater.

[0180] The present inventors have made extensive and intensive studieson lamination methods which can provide stable bonding strength. As aresult, they have confirmed that a predetermined bonding strength canalso be provided by a layer construction as shown in FIG. 2B(c), thatis, by coating an emulsion of an acid-modified polyolefin onto theconversion treated layer, drying and baking the coating (13 h), and thenstacking a film as a sealant layer by hot lamination.

[0181] Further, the present inventors have confirmed that stable bondingstrength can be provided by the following lamination method.

[0182] A laminate having predetermined bonding strength can be prepared,for example, by stacking a substrate layer 11 on one side of a barrierlayer 12 by dry lamination, and, as shown in FIG. 2B(a), FIG. 2B(b), andFIG. 2B(e), extruding an acid-modified polyolefin 13 e onto the otherside (conversion treated layer) of the barrier layer 12 to stack asealant layer 14 by sandwich lamination to prepare a laminate, oralternatively coextruding an acid-modified polyolefin resin 13 and asealant layer to prepare a laminate, and then heating the laminate at atemperature at or above the softening point of the acid-modifiedpolyolefin resin 13 e.

[0183] Specific examples of heating methods include a hot roll contactmethod, a hot air method, and a near-infrared or far-infrared method. Inthe present invention, any heating method may be used so far as, asdescribed above, the adhesive resin can be heated at a temperature at orabove the softening point thereof.

[0184] A laminate having stable bonding strength can also be prepared bya further method wherein, at the time of the above sandwich laminationor coextrusion lamination, heating is carried out so that thetemperature of the surface of the aluminum 12 on its sealant layer sidereaches the softening point of the acid-modified polyolefin resin.

[0185] In the packaging material for a battery according to the presentinvention, each of the layers constituting the laminate for armor bodyformation may be properly subjected to surface activation treatment,such as corona treatment, blast treatment, oxidation treatment, or ozonetreatment, from the viewpoints of improving or stabilizing film formingproperties, lamination, and suitability for fabrication of the finalproduct (pouching or emboss molding).

[0186] C. Third Aspect of the invention

[0187] 1. Specific Embodiments

[0188] Specific embodiments of the third aspect of the present inventionare as follows. Specifically, the invention as defined in claim 14provides a packaging material for forming an armor body for a battery,said armor body being adapted for use in such a manner that a batterybody is inserted into the armor body and the peripheral edge of thearmor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, aluminum, a conversion treated layer, an adhesive resinlayer, and a polypropylene resin-based sealant layer, characterized inthat the adhesive resin layer is formed of a resin having a melt indexin the range of 5 to 20 g/10 min. The invention as defined in claim 15is characterized in that the adhesive resin layer as defined in claim 14comprises a polypropylene resin. The invention as defined in claim 16 ischaracterized in that the adhesive resin layer as defined in claim 14 or15 comprises acid-modified polypropylene. The invention as defined inclaim 17 is characterized in that the adhesive resin layer as defined inclaim 14 comprises an acid-modified polyethylene resin and, added to theacid-modified polyethylene resin, at least one component selected from alow-density polypropylene resin, a low crystallineethylene-butene-propylene copolymer with a density of 900 kg/m³, anoncrystalline ethylene-propylene copolymer, a propylene-α-olefincopolymer, and a rubber component. The invention as defined in claim 18is characterized in that the adhesive resin layer as defined in claim 14is formed of a blend of at least two polypropylene resins with differentmelt indexes. The invention as defined in claim 19 is characterized inthat at least one of the at least two polypropylene resins constitutingthe adhesive resin layer as defined in claim 18 is an acid-modifiedpolypropylene resin. The invention as defined in claim 20 provides apackaging material for a battery wherein the laminate comprises thepackaging material for a battery as defined in any one of claims 14 to19 characterized by comprising at least the substrate layer, theadhesive layer, a conversion treated layer (1), aluminum, a conversiontreated layer (2), the adhesive resin layer, and the polypropyleneresin-based sealant layer. The invention as defined in claim 21 providesa battery wherein the battery body is housed and hermetically sealedinto an armor body formed of the packaging material for a battery asdefined in any one of claims 14 to 20.

[0189] 2. Embodiments of the Invention

[0190] The packaging material for a battery according to the presentinvention is a packaging material for an armor body for a battery,comprising at least a substrate layer, an adhesive layer, aluminum, aconversion treated layer, an adhesive resin layer, and a polypropyleneresin-based sealant layer comprising an acid-modified polyolefin layer,wherein at least the resin constituting the adhesive resin layer has amelt index in the range of 5 to 20 g/10 min. By virtue of the adoptionof this melt index, the insulation between the lead and the barrierlayer can be ensured, and root cutting can be advantageously prevented.The present invention will be described in more detail with reference tothe accompanying drawings and the like.

[0191]FIG. 3A is a diagram illustrating the packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing an embodiment of the layer construction ofthe packaging material for a battery, and (b) a cross-sectional viewshowing another embodiment of the layer construction of the packagingmaterial for a battery. FIG. 3B is a diagram illustrating the packagingmaterial for a battery according to the present invention, wherein (a)is a cross-sectional view showing the positional relationship betweenthe packaging material for a battery (the layer construction thereofbeing shown) and a lead, (b) a cross-sectional view illustrating thestate of contact of the lead with the armor body at the lead part beforeheat sealing, (c) a typical cross-sectional view of the lead part afterheat sealing, (d) a cross-sectional view showing the positionalrelationship among the packaging material for a battery (the layerconstruction of the packaging material being shown), a film for thelead, and the lead, (e) a cross-sectional view illustrating the state ofcontact among the lead, the film for the lead, and the armor body beforeheat sealing, and (f) a typical cross-sectional view of the lead partafter heat sealing. FIG. 3C is a perspective view illustrating apouch-type armor body for a battery. FIG. 3D is a perspective viewillustrating an emboss-type armor body for a battery. FIG. 3Eillustrates molding at the time of the formation of an emboss-type armorbody, wherein (a) is a perspective view, (b) shows an emboss-molded mainbody of an armor body, (c) is a cross-sectional view taken on lineX1-X1, and (d) is an enlarged view of Y1 part. FIG. 3F is a diagramillustrating a method for mounting a film for a lead in bonding betweenthe packaging material for a battery and the lead.

[0192] The capability of maintaining the performance of the battery bodyfor a long period of time is required of the armor body for a battery.For example, as shown in FIG. 3G(a), a packaging material 10′ for armorbody formation comprises a substrate layer 11′, a barrier layer 12′, asealant layer 14′ and the like stacked on top of one another by variouslamination methods. In particular, when the sealant layer in thelaminate constituting the armor body for a battery (hereinafter referredto as “armor body”) comprises a polyolefin resin or the like, and, inthis case, when an acid-modified polyolefin film is used in a portionwhere a lead 4′ exists, for example, as a film 6′ for a lead, in housingthe battery body in the armor body and hermetically sealing the assemblyby sealing the peripheral edge, as shown in FIG. 3G(b), both the sealantlayer 14′ in the armor body and the film 6′ for a lead are melted byheat and pressure for heat sealing and, further, upon the application ofpressure, the barrier layer 12′ in the armor body 10′ often comes intocontact with the lead 4 formed of a metal, resulting in short-circuitingS.

[0193] As shown in FIGS. 3H(a) to 3H(c), at the time of heat sealing ofthe peripheral edge of the armor body, very small root cutting C oftenoccurs in the sealant layer 14′ around the inner edge of the sealedpart. When the root cutting C occurs, the electrolysis solution comesinto direct contact with the barrier layer. This breaks insulation amongthe battery body 2′, the lead 4′, and the barrier layer 12′ andconsequently creates a potential difference. The potential differenceresults in the formation of throughholes in the barrier layer 12′ due tothe corrosion of the barrier layer 12′ and the formation of a reactionproduct of a metal ion as the electrolyte called “dendrite.” Theseunfavorable phenomena shorten the service life of the battery.

[0194] The present inventors have made extensive and intensive studieson the prevention of the short-circuiting and root cutting caused aroundthe sealed part and, as a result, have found that the above problem canbe solved by adopting such a construction that the packaging materialfor forming the armor body, for a battery, adapted for use in such amanner that a battery body is inserted into the armor body and theperipheral edge of the armor body is then heat sealed for hermeticsealing, is a laminate, as shown in FIG. 3A(a), comprising at least asubstrate layer 11, an adhesive layer 16, a barrier layer 12, aconversion treated layer 15, an adhesive resin layer 13, and a sealantlayer 14, or alternatively a laminate, as shown in FIG. 3B(b),comprising at least a substrate layer 11, an adhesive layer 16, aconversion treated layer 15 (1), aluminum 12, a conversion treated layer(2), an adhesive resin layer 13, and a sealant layer 14, wherein theadhesive resin layer is formed of a resin having a melt index in therange of 5 to 20 g/10 min. This has led to the completion of the presentinvention.

[0195] The resin for the formation of the adhesive resin layer in thepackaging material for a battery according to the present invention(hereinafter referred to as “adhesive resin”) is a resin which is usedfor laminating the barrier layer and the sealant layer onto top of eachother, the service life of the battery. The occurrence of the rootcutting C is considered attributable to the fact that, in the above heatsealing, the adhesive resin layer 13 and the sealant layer 14 in thesealed portion (these layers being collectively referred to as “heatfused layer Mx”) are likely to be crystallized, while the nonsealedportion remains in the noncrystalline state, whereby the resin at theboundary therebetween is unstable and is likely to cause root cutting C.

[0196] The adhesive resin layer in the packaging material for a batteryaccording to the present invention has a melt index of 5 to 20 g/10 min.The adhesive resin layer may not be formed of a single resin. Forexample, LDPE, a low crystalline ethylene-butene-propylene copolymerwith a density of not more than 900 kg/M³, a noncrystallineethylene-propylene copolymer, a propylene-α-olefin copolymer, and arubber component, such as butadiene, may be added to an acid-modifiedpolypropylene having good film forming properties and having a large MIvalue to bring the apparent melt index, which will be described later,to 5 to 20 g/10 min.

[0197] Further, the adhesive resin layer in the packaging material for abattery according to the present invention may have such a compositionthat two or more resins of the same type, for example, polypropyleneresins, different from each other in MI have been blended together. Inthis case, acid-modified polypropylene is used as at least any one ofthe polypropylene resins to ensure strength of bonding to thepolypropylene sealant. Here polypropylene in the polypropylene resin maybe homo-type polypropylene, random-type polypropylene, block-typepolypropylene, or a terpolymer resin which is apropylene-ethylene-butene copolymer. “Acid-modified” means that anunsaturated carboxylic acid has been graft polymerized.

[0198] In the present invention, when two or more resins are blendedtogether, the apparent MI of the resin blend is preferably in the rangeof 5 to 20 g/10 min. MI may be measured by the method specified in JIS K7210.

[0199] As described above, when the resin for adhesive resin layerformation has a melt index in the range of 5 to 20 g/10 min, forexample, as compared with the case where a resin having a melt index of22 to 30 is used as the adhesive resin, the flow of the heat seal resincan be reduced to maintain the layer thickness of the sealant layer and,in has a laminate strength high enough to ensure bonding to each of theabove layers, and has a melt index in the range of 5 to 20 g/10 min.

[0200] The melt index (hereinafter referred to as “MI”) is a value asmeasured according to JIS K 7210.

[0201] In the present invention, when the adhesive resin layer is asingle resin layer, the resin used is preferably an acid-modifiedpolyolefin, such as acid-modified polyethylene or acid-modifiedpolypropylene, metal-crosslinked polyethylene, a copolymer of ethylenewith an acrylic acid or methacrylic acid derivative, a copolymer ofethylene with vinyl acetate, or the like, wherein all of these polymershave an MI value in the range of 5 to 20 g/10 min.

[0202] When the packaging material for a battery is formed using anadhesive resin layer formed of a resin having a melt index (hereinafterreferred to as “MI”) of more than 20 g/10 min, short-circuiting occursin the lead part at the time of heat sealing in the packaging of abattery and, in addition, root cutting often occurs near the sealedpart. On the other hand, when the adhesive resin layer is formed of apolypropylene resin having a small melt index (hereinafter referred toas “MI”) of 0.3 to 3 g/10 min, the film forming speed at the time ofsandwich lamination and coextrusion lamination is disadvantageouslylowered, or otherwise the layer thickness becomes uneven and,consequently, a problem of uneven layer thickness occurs.

[0203] In the prior art, in sandwich lamination or coextrusionlamination, acid-modified polypropylene having a large melt index hasbeen used as an adhesive resin from the viewpoint of maintaining theproductivity. When a battery body is housed in an armor body formed of alaminate formed using this adhesive resin followed by heat sealing forhermetic sealing under conventional conditions of 190° C., 1.0 MPa, and3 sec, as shown in FIG. 3H(c), root cutting C occurs in a portion near aresin pool t formed in the joint part in the sealed part. As a result,an electrolysis solution permeates through the root cutting C and comesinto direct contact with the barrier layer 12. This breaks insulationbetween the metal of the lead 4 and the barrier layer and consequentlycreates a potential difference at that portion. The potential differenceoften results in the formation of throughholes due to the corrosion ofthe barrier layer 12 and the formation of a reaction product of a metalion as the electrolyte called “dendrite.” These unfavorable phenomenashorten addition, the adhesive resin layer after heat sealing. Forexample, as shown in FIG. 3B(a), FIG. 3B(b), and FIG. 3B(c), after heatsealing, the adhesive resin layer 13 and the sealant layer 14 stay in afilm form between the barrier layer 12 and the lead 4 to maintaininsulating properties. Further, as shown in FIG. 3B(d), FIG. 3B(e), andFIG. 3B(f), also in the case of interposition of a film 6 for a leadbetween the laminate 10 in the armor body and the lead 4, after heatsealing, even when the film 6 for a lead has been melted, the adhesiveresin layer 13 and the sealant layer 14 advantageously stay in a filmform between the barrier layer 12 and the lead 4 to maintain theinsulating properties. As a result, short-circuiting S between thebarrier layer 12 and the lead 4 can be prevented.

[0204] Further, the formation of a resin pool t formed near the inneredge of the sealed part and root cutting C caused at the end of theresin pool t can be prevented. In the present invention, since theadhesive resin layer has a small melt index of 5 to 20 g/10 min, whenheat sealing for hermetic sealing is carried out under the sameconditions as described above, the thickness of adhesive resin layer 13in the heat fused layer Mx is not reduced and, consequently, theoccurrence of the root cutting C can be advantageously prevented.

[0205] The packaging material for a battery is used for the formation ofan armor body for packaging a battery body, and types of the packagingmaterial may be divided according to the type of the armor body into apouch type as shown in FIG. 3 and an emboss type as shown in FIG. 3D(a),FIG. 3D(b), or FIG. 3D(c). The pouch type may be a bag type such as athree sided seal type, a four sided seal type, or a pillow type. FIG. 3shows a pillow type as an example of the type of the armor body.

[0206] In the emboss type, as shown in FIG. 3D(a), a concave portion maybe formed on one side of the armor body. Alternatively, a constructionmay be adopted wherein, as shown in FIG. 3D(b), a concave portion isformed on both sides of the armor body, a battery body is housed in thearmor body, and the four peripheral sides of the armor body are heatsealed to hermetically seal the assembly. Further, a construction mayalso be adopted wherein, as shown in FIG. 3D(c), a concave portion isformed on both sides of the armor body with a folded portion sandwiched,a battery is housed in the armor body, and the three sides of the armorbody are heat sealed. When the packaging material for a battery is of anemboss type, as shown in FIGS. 3E(a) to 3E(d), the stacked packagingmaterial 10 is subjected to press molding to form a concave portion 7.

[0207] As shown in FIG. 3A(a), the packaging material for a batteryaccording to the present invention is a laminate comprising at least asubstrate layer 11, an adhesive layer 16, aluminum 12, a conversiontreated layer 15, an adhesive layer 13 d, and a multilayered sealantlayer 14. When an armor body, which will be described later, is of anemboss type, as shown in FIG. 3A(b), the laminate preferably comprises asubstrate layer 11, an adhesive layer 16, a conversion treated layer 15(1), aluminum 12, a conversion treated layer 15 (2), an adhesive layer13 d, and a multilayered sealant layer 14.

[0208] In the present invention, bonding between the conversion treatedlayer in the barrier layer and the sealant layer in the lamination ofthe packaging material for a battery is carried out by a sandwichlamination method using an adhesive resin layer or a coextrusionlamination method. In this case, the following bonding stabilizationtreatment is preferably carried out from the viewpoint of preventingdelamination by hydrofluoric acid or the like evolved as a result of areaction of the electrolysis solution in a lithium ion battery or thelike with water.

[0209] A laminate having predetermined bonding strength, as shown inFIG. 3A(a), can be prepared, for example, by stacking a substrate layer11 on one side of a barrier layer 12 by dry lamination 16, and extrudingan acid-modified polyolefin 13 onto the other side (conversion treatedlayer 15) of the barrier layer 12 to stack a sealant layer 14 bysandwich lamination to prepare a laminate, or alternatively coextrudingan acid-modified polyolefin resin 13 and a sealant layer 14 to prepare alaminate, and then heating the laminate at a temperature at or above thesoftening point of the acid-modified polypropylene resin 13.

[0210] As shown in FIG. 3A(b), the conversion treated layer 15 may beprovided on both sides of the barrier layer 12. Specific examples ofheating methods include a hot roll contact method, a hot air method, anda near-infrared or far-infrared method. In the present invention, anyheating method may be used so far as, as described above, the adhesiveresin can be heated at a temperature at or above the softeningtemperature thereof. A laminate having stable bonding strength can alsobe prepared by a further method wherein, at the time of the abovesandwich lamination or coextrusion lamination, heating is carried out sothat the temperature of the surface of the aluminum 12 on its sealantlayer side reaches the softening point of the acid-modifiedpolypropylene resin.

[0211] The lead for a battery is formed of an elongated sheet or rodmetal. The sheet lead has a thickness of 50 to 2,000 μm and a width ofabout 2.5 to 20 mm and is formed of ALM, copper (Cu) (copper plated withnickel (Ni)), nickel or the like.

[0212] When the sealant layer in the packaging material for a batteryaccording to the present invention does not have heat adhesion to themetal, as shown in FIG. 3B(d) or FIG. 3F, a film 6 for a lead havingheat sealing properties on both the sealant layer 14 and the lead 4 atthe time of hermetic sealing should be interposed between the lead 4 inthe battery and the laminate 10. An example of a method for interposingthe film for a lead is as follows. As shown in FIGS. 3F(a) and 3F(b),the film 6 for a lead is placed on the upper side and the lower side ofthe hermetic sealing part of the lead 4 in the battery body 2 (in fact,the film being fixed by temporary sealing on the upper side and thelower side of the hermetic sealing part), and the battery body 2 isinserted into the armor body 5, followed by heat sealing in such a statethat the lead part is sandwiched, whereby the assembly is hermeticallysealed. Another example of a method for placing the film 6 for a lead onthe lead 4 is to wind a film 6 for a lead around the lead 4 at itspredetermined position, as shown in FIG. 3F(d) or FIG. 3F(e).

[0213] Specific examples of materials for the film 6 for a lead includeacid-modified polypropylene (unsaturated carboxylic acid-grafted randompropylene), metal-crosslinked polyethylene, a copolymer of ethylene withan acrylic acid or methacrylic acid derivative, and a copolymer ofethylene with vinyl acetate. These materials may be used solely, as ablend of two or more, or in other forms.

[0214] The layer thickness of the film 6 for a lead may be one-third ormore of the thickness of the lead 4 used. For example, when thethickness of the lead 4 is 100 μm, the total thickness of the film 6 fora lead may be about 30 μm or more.

[0215] The packaging material for a battery is used for the formation ofan armor body for packaging a battery body, and types of the packagingmaterial may be divided according to the type of the armor body into apouch type as shown in FIG. 3C and an emboss type as shown in FIG. 3D(a), FIG. 3D(b), or FIG. 3D(c). The pouch type may be a bag type such asa three sided seal type, a four sided seal type, or a pillow type. FIG.3C shows a pillow type as an example of the type of the armor body.

[0216] In the emboss type, as shown in FIG. 3D(a), a concave portion maybe formed on one side of the armor body. Alternatively, a constructionmay be adopted wherein, as shown in FIG. 3D(b), a concave portion isformed on both sides of the armor body, a battery body is housed in thearmor body, and the four peripheral sides of the armor body are heatsealed to hermetically seal the assembly. Further, a construction mayalso be adopted wherein, as shown in FIG. 3D(c), a concave portion isformed on both sides of the armor body with a folded portion sandwiched,a battery is housed in the armor body, and the three sides of the armorbody are heat sealed. When the packaging material for a battery is of anemboss type, as shown in FIGS. 3E(a) to 3E(d), the stacked packagingmaterial 10 is subjected to press molding to form a concave portion 7.

[0217] Next, each layer constituting the packaging material for abattery according to the present invention will be described. Thesubstrate layer 11 in the armor body is formed of an oriented polyesteror a nylon film. Polyester resins usable herein include polyethyleneterephthalate, polybutylene terephthalate, polyethylene naphthalate,polybutylene naphthalate, interpolyester, and polycarbonate. Nylonsusable herein include polyamide resins, that is, nylon 6, nylon 6, 6, acopolymer of nylon 6 with nylon 6, 6, nylon 6, 10, andpoly-m-xylyleneadipamide (MXD 6).

[0218] When the substrate layer 11 is used as a battery, the substratelayer 11 is a site which comes into direct contact with the hardware.Therefore, basically, the substrate layer 11 is preferably a resin layerhaving insulating properties. When the presence of pinholes in the filmper se, the occurrence of pinholes at the time of fabrication and thelike are taken into consideration, the substrate layer should have athickness of not less than 6 μm, preferably 12 to 30 μm.

[0219] In order to improve anti-pinhole properties and insulatingproperties of the armor body for a battery, the substrate layer 11 maybe in the form of a laminate.

[0220] When the substrate layer is in the form of a laminate, thesubstrate layer includes at least one unit of two or more resin layersand, in this case, the thickness of each layer is not less than 6 μm,preferably 12 to 30 μm. Examples of the substrate layer having amultilayer structure include the following layer constructions 1) to 8).

[0221] 1) Oriented polyethylene terephthalate/oriented nylon, and

[0222] 2) Oriented nylon/oriented polyethylene terephthalate.

[0223] Further, from the viewpoint of machinability (stable carriage ina packaging machine or a processing machine) of the packaging material,surface protective properties (heat resistance and electrolyteresistance), a reduction in frictional resistance between the mold andthe substrate layer at the time of embossing to form an emboss-typearmor body for a battery by fabrication, or protection of the substratelayer upon the deposition of an electrolysis solution, preferably, thesubstrate layer has a multilayer structure, and a fluororesin layer, anacrylic resin layer, a silicone resin layer, a polyester resin layer, aresin layer formed of a blend of two or more of the above materials orthe like is provided on the surface of the substrate layer. Examples ofthis type of substrate layer include

[0224] 3) fluororesin/oriented polyethylene terephthalate (thefluororesin layer is constituted by a fluororesin film or is formed byliquid coating and then drying),

[0225] 4) silicone resin/oriented polyethylene terephthalate (thesilicone resin layer is constituted by a silicone resin film or isformed by liquid coating and then drying),

[0226] 5) fluororesin/oriented polyethylene terephthalate/orientednylon,

[0227] 6) silicone resin/oriented polyethylene terephthalate/orientednylon,

[0228] 7) acrylic resin/oriented nylon (the acrylic resin layer isconstituted by an acrylic resin film or is formed by liquid coating andthen drying for curing), and

[0229] 8) acrylic resin+polysiloxane-grafted acrylic resin/orientednylon (the acrylic resin layer is constituted by an acrylic resin filmor is formed by liquid coating and then drying for curing).

[0230] The barrier layer 12 is a layer for preventing the entry ofparticularly water vapor in the battery from the exterior. From theviewpoints of pinholes in the barrier layer per se and stabilization offabricability (pouching or emboss moldability) and of impartinganti-pinhole properties, not less than 15 μm-thick aluminum, nickel orother metal, or a film with an inorganic compound, for example, siliconoxide or alumina, vapor deposited thereon may be mentioned as thebarrier layer. Preferably, however, the barrier layer is 20 to 80-μmthick aluminum.

[0231] When a further reduction in occurrence of pinholes and theformation of an emboss-type armor body for a battery are contemplated,studies conducted by the present inventors have revealed that, in orderto prevent cracking and the like at the time of emboss molding, when thebarrier layer is formed of aluminum having an iron content of 0.3 to9.0% by weight, preferably 0.7 to 2.0% by weight, as compared withiron-free aluminum, the iron-containing aluminum has better ductilityand the occurrence of pinholes of the laminate by folding can be reducedand, at the same time, the formation of the side wall at the time ofmolding of the emboss-type armor body is easier. When the iron contentis less than 0.3% by weight, for example, the effect of preventing theoccurrence of pinholes and the effect of improving emboss moldabilitycannot be attained. On the other hand, when the iron content of thealuminum exceeds 9.0% by weight, the flexibility as the aluminum ishindered and the suitability of the laminate for bag making isdeteriorated.

[0232] For aluminum produced by cold rolling, the flexibility, thenerve, and the hardness vary depending upon conditions for annealingtreatment. For aluminum used in the present invention, somewhat or fullyannealed aluminum, which is relatively soft, is preferred rather than ahardening treated product not subjected to annealing.

[0233] The flexibility, nerve, and hardness of aluminum, that is,conditions for annealing, may be properly selected according tosuitability for fabrication (pouching or emboss molding). For example,in order to prevent the occurrence of wrinkles and pinholes at the timeof emboss molding, the use of soft aluminum, which has been annealeddepending upon the degree of molding, is preferred.

[0234] The present inventors have found that, when conversion treatmentis carried out on the front and back sides of aluminum as the barrierlayer 12 in the packaging material for a battery, a laminate, which issatisfactory as the packaging material, can be provided. Specifically,the conversion treatment refers to the formation of an acid-resistantfilm of a salt of phosphoric acid, a salt of chromic acid, a fluoride, atriazinethiol compound or the like. Phosphoric acid chromate treatmentusing a three-component system of a phenolic resin, a chromium(III)fluoride compound, and phosphoric acid among the above acid-resistantfilm forming materials can provide good results. Further, a conversiontreating agent comprising a resin component containing at least aphenolic resin and, added thereto, a metal, such as molybdenum,titanium, or zirconium, or a metal salt can provide good results.Advantageously, the formation of the acid-resistant film can preventdelamination between the aluminum and the substrate layer at the time ofemboss molding, can prevent dissolution and corrosion of the surface ofaluminum, particularly dissolution and corrosion of aluminum oxidepresent on the surface of the aluminum, by hydrogen fluoride produced asa result of a reaction of an electrolyte in the battery with water, canimprove the adhesion (wettability) of the surface of aluminum, canprevent delamination between the substrate layer 11 and the aluminum 12at the time of emboss molding and heat sealing, and can preventdelamination on the inner side of the aluminum by hydrogen fluorideproduced as a result of a reaction of the electrolyte with water.

[0235] The present inventors have carried out conversion treatment ofthe surface of the aluminum using various materials and have madestudies on the effect of the conversion treatment. As a result, it wasfound that phosphoric acid chromate treatment using a three-componentsystem of a phenolic resin, a chromium(III) fluoride compound, andphosphoric acid among the above acid-resistant film forming materialscan provide good results.

[0236] Further, a conversion treating agent comprising a resin componentcontaining at least a phenolic resin and, added thereto, a metal, suchas molybdenum, titanium, or zirconium, or a metal salt can provide goodresults.

[0237] When the armor body is of a pouch type, the conversion treatmentof aluminum may be carried out on one side (only sealant layer side) ofthe aluminum or both sides (substrate layer side and sealant layer side)of the aluminum. On the other hand, when the armor body of the batteryis of an emboss type, conversion treatment of both sides of the aluminumcan prevent delamination between the aluminum and the substrate layer atthe time of emboss molding.

[0238] As described above, the adhesive resin layer 13 is a resin whichis melt extruded at the time of the lamination of the barrier layer 12and the sealant layer 14 by sandwich lamination or coextrusionlamination and has an MI value in the range of 5 to 20.

[0239] The sealant layer in the packaging material for a batteryaccording to the present invention may be formed of a polyethyleneresin, a polypropylene resin or the like. Polypropylene resins usableherein include, for example, homo-type polypropylene, random-typepolypropylene, and block-type polypropylene. If necessary, the sealantlayer may have a multilayer structure of two or more layers. The totalthickness of the sealant layer is suitably 20 to 200 μm.

[0240] D. Fourth Aspect of the Invention

[0241] 1. Specific Embodiments

[0242] Specific embodiments of the fourth aspect of the presentinvention are as follows. The invention as defined in claim 22 providesa packaging material for forming an armor body for a battery, said armorbody being adapted for use in such a manner that a battery body isinserted into the armor body and the peripheral edge of the armor bodyis then heat sealed for hermetic sealing, said packaging material beinga laminate comprising at least a substrate layer, an adhesive layer 1, abarrier layer, an adhesive layer 2, and a sealant layer, characterizedin that the sealant layer comprises one resin layer or a laminate of twoor more resin layers comprising metallocene linear low-densitypolyethylene. The invention as defined in claim 23 is characterized inthat the sealant layer as defined in claim 22 is formed of a metallocenelinear low-density polyethylene resin. The invention as defined in claim24 is characterized in that the sealant layer as defined in claim 21 isformed of a polyethylene resin containing not less than 10% of ametallocene linear low-density polyethylene resin. The invention asdefined in claim 25 is characterized in that the sealant layer asdefined in claim 22 has a multilayer structure comprising at least alayer formed of a metallocene linear low-density polyethylene resin. Theinvention as defined in claim 26 is characterized in that the sealantlayer as defined in claim 21 has a multilayer structure comprising apolyethylene resin layer containing not less than 10% of a metallocenelinear low-density polyethylene resin. The invention as defined in claim27 is characterized in that the adhesive layer 2 as defined in claim 22has been formed by dry lamination. The invention as defined in claim 28is characterized in that the adhesive layer 2 as defined in claim 22 isan acid-modified polyolefin coating-baked layer. The invention asdefined in claim 29 is characterized in that the adhesive layer 2 asdefined in claim 22 is an extruded layer of an acid-modified polyolefin.

[0243] 2. Embodiments of the Invention

[0244] The packaging material for a battery according to the presentinvention is a packaging material for forming an armor body for abattery. The packaging material comprises at least a substrate layer, anadhesive layer, a conversion treated layer 1, aluminum, a conversiontreated layer 2, an adhesive layer, and a sealant layer, wherein thesealant layer comprises at least a metallocene linear low-densitypolyethylene (hereinafter referred to as “metallocene LLDPE”) resin.According to this construction, stable emboss moldability andsuitability for sealing can be realized.

[0245] Further, a packaging material free from delamination is providedby the adoption of a specific method for laminating aluminum and asealant layer onto top of each other. The present invention will bedescribed in more detail with reference to the accompanying drawings andthe like.

[0246]FIG. 4A is an explanatory view of the packaging material for abattery according to the present invention, wherein (a) is across-sectional view showing an embodiment of a laminate and (b) across-sectional view showing another embodiment of the laminate. FIG. 4Bis a diagram illustrating the construction of a sealant layer, wherein(a) is a cross-sectional view of a sealant layer having a single-layerstructure, (b) a cross-sectional view of a sealant layer having atwo-layer structure, and (c) a cross-sectional view of a sealant layerhaving a three-layer structure. FIG. 4C is a cross-sectional view ofpackaging materials for a battery according to the present inventionwhich are different from one another in lamination method used for theformation thereof, wherein (a) is a diagram showing a packaging materialformed by dry lamination, (b) a diagram showing a packaging materialformed by hot lamination, (c) a diagram showing a packaging materialformed by sandwich lamination, and (d) a diagram showing a packagingmaterial formed by coextrusion lamination. FIG. 4D is a perspective viewillustrating a pouch-type armor body for a battery. FIG. 4E is aperspective view illustrating an emboss-type armor body for a battery.FIG. 4F illustrates molding at the time of the formation of anemboss-type armor body, wherein (a) is a perspective view, (b) a diagramshowing an emboss-molded main body of an armor body, (c) across-sectional view taken on line X2-X2, and (d) an enlarged view of Y1part.

[0247] The packaging material for a battery comprises a laminatecomprising at least a substrate layer, a barrier layer, and a sealantlayer. It has been confirmed that the interlaminar bonding strengthamong the above layers affects properties required of the armor body ofthe battery. For example, unsatisfactory bonding strength between thebarrier layer and the sealant layer is causative of the entry of waterfrom the exterior. The entry of water causes the corrosion of thealuminum face by hydrofluoric acid produced by a reaction of theelectrolyte in the components constituting the battery with the abovewater and consequently causes delamination between the barrier layer andthe sealant layer. Further, in the formation of the emboss-type armorbody, at the time of press molding of the laminate to form a concaveportion, delamination between the substrate layer and the barrier layeroften occurs.

[0248] As shown in FIG. 4A(a), the packaging material for a battery is alaminate comprising at least a substrate layer 11, an adhesive layer 16,aluminum 12, a conversion treated layer 15, an adhesive layer 13, and asealant layer 14. In the case of the emboss-type armor body, as shown inFIG. 4A(b), the laminate preferably comprises a substrate layer 11, anadhesive layer 16, a conversion treated layer 15 (1), aluminum 12, aconversion treated layer 15 (2), an adhesive layer 13, and a sealantlayer 14.

[0249] In the case of the emboss-type armor body, when a resin having ahigh tensile modulus of elasticity is used in the sealant layer, at thetime of emboss molding, the sealant layer often undergoes whitening orslight cracking in its surface. Further, the molding stability is poor,and pinholes, molding wrinkling, or cracks often occur.

[0250] Further, hermetical sealing properties after filling of thecontents and sealing may be mentioned as properties which areindispensable as the packaging material for a battery. For example, whenthe seal strength of the packaging material is low, a satisfactory timeis necessary for sealing in a content filling/sealing line. Thissignificantly hinders cycle shortening and often deteriorates theproduction efficiency.

[0251] The present inventors have made extensive and intensive studiesand, as a result, have found that the above problems can be solved whenthe packaging material for forming an armor body, for a battery, adaptedfor use in such a manner that a battery body is inserted into the armorbody and the peripheral edge of the armor body is heat sealed forhermetic sealing, is a laminate, as shown in FIG. 4A(a), comprising, forexample, a substrate layer 11, an adhesive layer 16, a barrier layer 12,a conversion treated layer 15, an adhesive resin layer 13, and a sealantlayer 14, wherein the sealant layer 14 comprises one resin layer or alaminate of two or more resin layers comprising metallocene linearlow-density polyethylene. This has led to the completion of the presentinvention.

[0252] The metallocene linear low-density polyethylene refers topolyethylene which has been polymerized in the presence of a metallocenecatalyst (a single-site catalyst) and, as compared with the conventionallinear low-density polyethylene, is smaller in the number of branches inthe side chain and is more uniform in distribution of molecular weightand comonomers. Therefore, the metallocene linear low-densitypolyethylene has excellent properties such as high transparency, lowmelting point, and high impact resistance.

[0253] The sealant layer in the packaging material for a batteryaccording to the present invention will be described. In the sealantlayer, as shown in FIG. 4B(a), a resin layer containing the metallocenelinear low-density polyethylene may be a single layer S formed of ametallocene linear low-density polyethylene resin (hereinafter referredto as “MLL”) or may be a single layer S formed of a polyethylene resinblended with not less than 10% by weight of MLL. In the case of theMLL-blended polyethylene resin, when the MLL blending ratio is less than10% by weight, the effect of improving moldability, which is to beattained by the present invention, cannot be developed.

[0254] The sealant layer in the packaging material for a batteryaccording to the present invention may have a two-layer structure of theabove resin layer S3 formed of MLL and another resin layer S2 formed ofMLL as shown in FIG. 4B(b), or alternatively may have a three-layerstructure of the above resin layers S3 and S2 and a further layer Siformed of MLL as shown in FIG. 4B(c). The resin layers S1 to S3 eachformed of MLL may be MLL-blended polyethylene resin layers. In thiscase, however, the resin layer S3 as the innermost layer is preferablyformed of MLL.

[0255] In the present invention, as shown in FIG. 4B(b) or FIG. 4B(c),when the sealant layer 14 has a multilayer structure of an MLL layer S3or a blend resin layer S3 containing not less than 10% by weight of theMLL resin and the other layers S1 and S2, the resin constituting theother layers S1 and S2 may be, for example, a low-density polyethyleneresin, a medium-density polyethylene resin, a high-density polyethyleneresin, a polypropylene resin, or an acid-modified polyolefin that is anyone of the above resins onto which an unsaturated carboxylic acid hasbeen grafted.

[0256] In the present invention, when the sealant layer 14 has amultilayer structure of an MLL layer or a blend resin layer (hereinafterreferred to as “MLL-blended layer”) containing not less than 10% byweight of the MLL resin and other layer(s), the thickness of the MLLlayer or the MLL-blended layer is preferably not less than 15% of thetotal thickness of the sealant layer. When the thickness of the MLLlayer or the MLL-blended layer is less than 15% of the total thicknessof the sealant layer, the effect of improving the moldability is notdeveloped.

[0257] In the formation of the laminate for the packaging material for abattery according to the present invention, the barrier layer and thesealant layer may be laminated onto top of each other, for example, bydry lamination, sandwich lamination, coextrusion lamination, or hotlamination.

[0258] The present inventors have made extensive and intensive studieson lamination methods which can provide stable bonding strength. As aresult, they have confirmed that predetermined bonding strength can alsobe provided by the following methods. Specifically, a barrier layer 12,in which at least a surface to be laminated with a sealant layer hasbeen conversion treated, and a substrate layer 11 are laminated onto topof each other by dry lamination. The sealant layer is then laminatedonto the conversion treated layer provided on the barrier layer by abonding method, as shown in FIG. 4C(a), wherein they are laminated (13d) by dry lamination, or by a bonding method, as shown in FIG. 4C(b),wherein an emulsion of acid-modified polyethylene is coated onto theconversion treated layer, the coating is dried and baked (13 h), and ametallocene LLDPE film as a sealant layer is then stacked onto the bakedlayer by hot lamination.

[0259] The present inventors have further confirmed that stable bondingstrength can also be provided by the following lamination methods.

[0260] Specifically, a substrate layer 11 is laminated by dry laminationonto one side of a barrier layer 12 with both sides thereof beingconversion treated. Thereafter, as shown in FIG. 4C(c), acid-modifiedpolyethylene 13 es is extruded on the other side of the barrier layer 12to laminate a sealant layer 14 by sandwich lamination, or alternatively,as shown in FIG. 4C(d), an acid-modified polyethylene resin 13 ec and ametallocene LLDPE resin as a sealant layer 14 are coextruded. Thus, alaminate is prepared. The laminate is then heated to such a state thatthe acid-modified polyethylene resin reaches a temperature at or abovethe softening point of the acid-modified polyethylene resin.

[0261] Specific examples of heating methods include a hot roll contactmethod, a hot air method, and a near-infrared or far-infrared method. Inthe present invention, any heating method may be used so far as, asdescribed above, the adhesive resin can be heated at a temperature at orabove the softening point thereof.

[0262] A laminate having stable bonding strength can also be prepared bya further method wherein, at the time of the above sandwich laminationor coextrusion lamination, heating is carried out so that thetemperature of the surface of the aluminum 12 on its sealant layer sidereaches the softening point of the acid-modified polyolefin resin 13 e.The polyethylene resin may be used as the adhesive resin. In this case,a useful lamination method is that lamination is carried out whilesubjecting an extruded melted polyethylene resin film on its laminationface in the aluminum side to ozone treatment.

[0263] Another lamination method is that a substrate layer 11 islaminated by dry lamination onto one side of a barrier layer 12 withboth sides thereof being conversion treated, as shown in FIG. 4C(c),only acid-modified polyethylene 13 es is extruded onto the other side ofthe barrier layer 12 to prepare an intermediate laminate, and theintermediate laminate is heated to such a state that the temperature ofthe acid-modified polyethylene resin reaches the softening point thereofor above, followed by extrusion of a metallocene LLDPE resin as asealant layer 14 to prepare a laminate. The above extrusion, which iscarried out twice, may be carried out in an in-line manner using atandem machine, or alternatively may be carried out in an off-linemanner using a conventional extruder.

[0264] The heating may be carried out after the extrusion of themetallocene LLDPE resin. However, heating after the extrusion of theacid-modified polyethylene 13 es (before the extrusion of themetallocene LLDPE resin) is preferred, because the slipperiness of thesealant layer 14 in the laminate is not deteriorated and, thus, embossmoldability can be further improved.

[0265] As described above, according to the present invention, by virtueof the adoption of the above specific lamination method, delaminationbetween the barrier layer and the sealant layer (or the adhesive resinlayer) can be prevented. Further, the formation of the sealant layerusing metallocene LLDPE or a metallocene LLDPE-containing resin canprevent the formation of wrinkles, pinholes and the like in the embossmolding process. Further, the use of the above sealant can providehigher seal strength than the use of the conventional LLDPE. Therefore,the present invention can offer very good molding quality andproductivity improvement effects such as an improvement in hermeticalsealing properties and cycle shortening in the filling/sealing process.

[0266] The packaging material for a battery is used for the formation ofan armor body for packaging a battery body, and types of the packagingmaterial may be divided according to the type of the armor body into apouch type as shown in FIG. 4D and an emboss type as shown in FIG. 4E(a), FIG. 4E(b), or FIG. 4E(c). The pouch type may be a bag type such asa three sided seal type, a four sided seal type, or a pillow type. FIG.4D shows a pillow type as an example of the type of the armor body.

[0267] In the emboss type, as shown in FIG. 4E(a), a concave portion maybe formed on one side of the armor body. Alternatively, a constructionmay be adopted wherein, as shown in FIG. 4E(b), a concave portion isformed on both sides of the armor body, a battery body is housed in thearmor body, and the four peripheral sides of the armor body are heatsealed to hermetically seal the assembly. Further, a construction mayalso be adopted wherein, as shown in FIG. 4E(c), a concave portion isformed on both sides of the armor body with a folded portion sandwiched,a battery is housed in the armor body, and the three sides of the armorbody are heat sealed. When the packaging material for a battery is of anemboss type, as shown in FIGS. 4F(a) to 4F(d), the stacked packagingmaterial 10 is subjected to press molding to form a concave portion 7.

[0268] Next, each layer constituting the packaging material for abattery according to the present invention will be described.

[0269] The substrate layer 11 in the armor body is formed of an orientedpolyester or a nylon film. Polyester resins usable herein includepolyethylene terephthalate, polybutylene terephthalate, polyethylenenaphthalate, polybutylene naphthalate, interpolyester, andpolycarbonate. Nylons usable herein include polyamide resins, that is,nylon 6, nylon 6, 6, a copolymer of nylon 6 with nylon 6, 6, nylon 6,10, and poly-m-xylyleneadipamide (MXD 6).

[0270] When the substrate layer 11 is used as a battery, the substratelayer 11 is a site which comes into direct contact with the hardware.Therefore, basically, the substrate layer 11 is preferably a resin layerhaving insulating properties. When the presence of pinholes in the filmper se, the occurrence of pinholes at the time of fabrication and thelike are taken into consideration, the substrate layer should have athickness of not less than 6 μm, preferably 12 to 30 μm.

[0271] In order to improve anti-pinhole properties and insulatingproperties of the armor body for a battery, the substrate layer 11 maybe in the form of a laminate.

[0272] When the substrate layer is in the form of a laminate, thesubstrate layer includes at least one unit of two or more resin layersand, in this case, the thickness of each layer is not less than 6 μm,preferably 12 to 30 μm. Examples of the substrate layer having amultilayer structure include the following layer constructions 1) to 8).

[0273] 1) Oriented polyethylene terephthalate/oriented nylon, and

[0274] 2) Oriented nylon/oriented polyethylene terephthalate. Further,from the viewpoint of machinability (stable carriage in a packagingmachine or a processing machine) of the packaging material, surfaceprotective properties (heat resistance and electrolyte resistance), areduction in frictional resistance between the mold and the substratelayer at the time of embossing to form an emboss-type armor body for abattery by fabrication, or protection of the substrate layer upon thedeposition of an electrolysis solution, preferably, the substrate layerhas a multilayer structure, and a fluororesin layer, an acrylic resinlayer, a silicone resin layer, a polyester resin layer, a resin layerformed of a blend of two or more of the above materials or the like isprovided on the surface of the substrate layer. Examples of this type ofsubstrate layer include

[0275] 3) fluororesin/oriented polyethylene terephthalate (thefluororesin layer is constituted by a fluororesin film or is formed byliquid coating and then drying),

[0276] 4) silicone resin/oriented polyethylene terephthalate (thesilicone resin layer is constituted by a silicone resin film or isformed by liquid coating and then drying),

[0277] 5) fluororesin/oriented polyethylene terephthalate/orientednylon,

[0278] 6) silicone resin/oriented polyethylene terephthalate/orientednylon,

[0279] 7) acrylic resin/oriented nylon (the acrylic resin layer isconstituted by an acrylic resin film or is formed by liquid coating andthen drying for curing), and

[0280] 8) acrylic resin+polysiloxane-grafted acrylic resin/orientednylon (the acrylic resin layer is constituted by an acrylic resin filmor is formed by liquid coating and then drying for curing).

[0281] The barrier layer 12 is a layer for preventing the entry ofparticularly water vapor in the battery from the exterior. From theviewpoints of pinholes in the barrier layer per se and stabilization offabricability (pouching or emboss moldability) and of impartinganti-pinhole properties, not less than 15 μm-thick aluminum, nickel orother metal, or a film with an inorganic compound, for example, siliconoxide or alumina, vapor deposited thereon may be mentioned as thebarrier layer. Preferably, however, the barrier layer is 20 to 80-μmthick aluminum.

[0282] When a further reduction in occurrence of pinholes and theformation of an emboss-type armor body for a battery are contemplated,studies conducted by the present inventors have revealed that, in orderto prevent cracking and the like at the time of emboss molding, when thebarrier layer is formed of aluminum having an iron content of 0.3 to9.0% by weight, preferably 0.7 to 2.0% by weight, as compared withiron-free aluminum, the iron-containing aluminum has better ductilityand the occurrence of pinholes of the laminate by folding can be reducedand, at the same time, the formation of the side wall at the time ofmolding of the emboss-type armor body is easier. When the iron contentis less than 0.3% by weight, for example, the effect of preventing theoccurrence of pinholes and the effect of improving emboss moldabilitycannot be attained. On the other hand, when the iron content of thealuminum exceeds 9.0% by weight, the flexibility as the aluminum ishindered and the suitability of the laminate for bag making isdeteriorated.

[0283] For aluminum produced by cold rolling, the flexibility, thenerve, and the hardness vary depending upon conditions for annealingtreatment. For aluminum used in the present invention, somewhat or fullyannealed aluminum, which is relatively soft, is preferred rather than ahardening treated product not subjected to annealing.

[0284] The present inventors have found that, when conversion treatmentis carried out on the front and back sides of aluminum as the barrierlayer 12 in the packaging material for a battery, a laminate, which issatisfactory as the packaging material, can be provided. Specifically,the conversion treatment refers to the formation of an acid-resistantfilm of a salt of phosphoric acid, a salt of chromic acid, a fluoride, atriazinethiol compound or the like. Phosphoric acid chromate treatmentusing a three-component system of a phenolic resin, a chromium(III)fluoride compound, and phosphoric acid among the above acid-resistantfilm forming materials can provide good results. Further, a conversiontreating agent comprising a resin component containing at least aphenolic resin and, added thereto, a metal, such as molybdenum,titanium, or zirconium, or a metal salt can provide good results.Advantageously, the formation of the acid-resistant film can preventdelamination between the aluminum and the substrate layer at the time ofemboss molding, can prevent dissolution and corrosion of the surface ofaluminum, particularly dissolution and corrosion of aluminum oxidepresent on the surface of the aluminum, by hydrogen fluoride produced asa result of a reaction of an electrolyte in the battery with water, canimprove the adhesion (wettability) of the surface of aluminum, canprevent delamination between the substrate layer 11 and the aluminum 12at the time of emboss molding and heat sealing, and can preventdelamination on the inner side of the aluminum by hydrogen fluorideproduced as a result of a reaction of the electrolyte with water.

[0285] The present inventors have carried out conversion treatment ofthe surface of the aluminum using various materials and have madestudies on the effect of the conversion treatment. As a result, it wasfound that phosphoric acid chromate treatment using a three-componentsystem of a phenolic resin, a chromium(III) fluoride compound, andphosphoric acid among the above acid-resistant film forming materialscan provide good results.

[0286] Further, a conversion treating agent comprising a resin componentcontaining at least a phenolic resin and, added thereto, a metal, suchas molybdenum, titanium, or zirconium, or a metal salt can provide goodresults.

[0287] When the armor body is of a pouch type, the conversion treatmentof aluminum may be carried out on one side (only sealant layer side) ofthe aluminum or both sides (substrate layer side and sealant layer side)of the aluminum. On the other hand, when the armor body of the batteryis of an emboss type, conversion treatment of both sides of the aluminumcan prevent delamination between the aluminum and the substrate layer atthe time of emboss molding. In the packaging material for a batteryaccording to the present invention, the adhesive resin used forlamination of the barrier layer and the sealant layer onto top of eachother by sandwich lamination or coextrusion lamination is preferablyacid-modified polyethylene. The acid-modified polyethylene ispolyethylene onto which an unsaturated carboxylic acid has been graftpolymerized. The acid-modified polyethylene has good adhesion to boththe surface of the conversion treated layer in the barrier layer and theresin in the lamination surface of the sealant layer.

[0288] As described above, the sealant layer in the packaging materialfor a battery according to the present invention may have a single-layerstructure of a metallocene PE resin, a single-layer structure of ametallocene PE-blended resin, or a multilayer structure containing atleast the above single layer.

[0289] In the present invention, each of the layers constituting thelaminate for armor body formation may be properly subjected to surfaceactivation treatment, such as corona treatment, blast treatment,oxidation treatment, or ozone treatment, from the viewpoints ofimproving or stabilizing film forming properties, lamination, andsuitability for fabrication of the final product (pouching or embossmolding).

EXAMPLE

[0290] A. First Aspect of invention

[0291] The packaging material for a battery according to the firstaspect of the present invention will be described in more detail withreference to the following examples.

[0292]5<Common Conditions A>

[0293] Conditions common to Example A and Comparative Example A are asfollows.

[0294] (1) Armor Body

[0295] In the following Example A and Comparative Example A, the size ofa pouch-type armor body was 30 mm in width (inside dimension)×50 mm inlength inside dimension). In the case of an emboss-type armor body, onlyone side was embossed, and moldability was evaluated by press moldingusing a mold having a concave (a cavity) having a size of 30 mm×50 mmand a depth of 3.5 mm.

[0296] (2) Total Thickness of Sealant Layer

[0297] In all cases, the total thickness of a sealant layer was 30 μm.

[0298] (3) Conversion Treatment

[0299] For both Example A and Comparative Example A, the conversiontreatment of a barrier layer in the armor body was carried out asfollows. An aqueous solution composed of a phenolic resin, achromium(III) fluoride compound, and phosphoric acid was provided as atreatment liquid. The treatment liquid was roll coated onto the barrierlayer, and the coating was baked under conditions such that the filmtemperature was 180° C. or above. The coverage of chromium was 2 mg/m²on a dry weight basis.

[0300] (4) Lead and Film for Lead

[0301] For both Example A and Comparative Example A, a lead having athickness of 100 μm, a width of 6 mm, and a length of 25 mm was used.For both Example A and Comparative Example A, a 30-μm acid-modifiedpolypropylene film was provided as a film for a lead, was wound around apredetermined position of the lead for the battery body, and the batterybody was then inserted into the armor body.

[0302] (5) Conditions for Heat Sealing

[0303] Heat sealing was carried out under conditions of 190° C., 1 MPa,and 3 sec.

[0304] However, only for the evaluation of short-circuiting, heatsealing was carried out under conditions of 190° C., 2 MPa, and 5 sec.

Example A1

[0305] Both sides of 20 μm-thick aluminum were subjected to conversiontreatment, and an oriented polyester film (thickness 12 μm) waslaminated onto one conversion treated side of the aluminum by drylamination. Next, a sealant layer was laminated onto the otherconversion treated side of the aluminum by dry lamination. A pillow-typepouch as an armor body was formed using the laminate thus obtained.

[0306] The sealant layer had a two-layer structure of low-fluidity PP<6>/high-fluidity PP (inner side)<4>. These PPs had the following MI andmelting point. Figures in brackets indicate layer thickness ratio incoextruded multilayer. This is true of Example A and Comparative ExampleA which will be described later.

[0307] Low-fluidity PP: MI 0.59/10 min, m.p. 147° C.

[0308] High-fluidity PP: MI 20 g/10 min, m.p. 160° C.

[0309] A battery body was inserted into the above armor body, and theassembly was then heat sealed for hermetic sealing to prepare a sampleof Example A1.

Example A2

[0310] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by dry lamination. A tray was formed by embossmolding using the laminate thus obtained. An emboss-type armor body wasprepared using this tray and the unmolded laminate as a lid.

[0311] The sealant layer had a two-layer structure of low-fluidity PP<9>/high-fluidity PP (inner side)<1>. These PPs had the following MI andmelting point.

[0312] Low-fluidity PP: MI 3 g/10 min, m.p. 147° C.

[0313] High-fluidity PP: MI 7 g/10 min, m.p. 147° C.

[0314] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of Example A2.

Example A3

[0315] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by dry lamination. A tray was formed by embossmolding using the laminate thus obtained. An emboss-type armor body wasprepared using this tray and the unmolded laminate as a lid.

[0316] The sealant layer had a three-layer structure of high-fluidity PP{circle over (1)} <1>/low-fluidity PP <8>/high-fluidity PP (inner side){circle over (2)} <1>. These PPs had the following MI and melting point.

[0317] High-fluidity PP {circle over (1)}: MI 10 g/10 min, m.p. 147° C.

[0318] Low-fluidity PP: MI 1 g/10 min, m.p. 160° C.

[0319] High-fluidity PP {circle over (2)}: MI 10 g/10 min, m.p. 147° C.

[0320] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of Example A3.

Example A4

[0321] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by dry lamination. A tray was formed by embossmolding using the laminate thus obtained. An emboss-type armor body wasprepared using this tray and the unmolded laminate as a lid.

[0322] The sealant layer had a three-layer structure of high-fluidity PP{circle over (1)} <1>/low-fluidity PP <6>/high-fluidity PP (inner side){circle over (2)} <3>. These PPs had the following MI and melting point.

[0323] High-fluidity PP {circle over (1)}: MI 20 g/10 min, m.p. 147° C.

[0324] Low-fluidity PP: MI 3 g/10 min, m.p. 160° C.

[0325] High-fluidity PP {circle over (2)}: MI 8, m.p. 147° C.

[0326] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of Example A4.

Comparative Example A1

[0327] Both sides of 20 μm-thick aluminum were subjected to conversiontreatment, and an oriented polyester film (thickness 12 μm) waslaminated onto one conversion treated side of the aluminum by drylamination. Next, a sealant layer was laminated onto the otherconversion treated side of the aluminum by dry lamination. A pillow-typepouch as an armor body was formed using the laminate thus obtained.

[0328] The sealant layer had a two-layer structure of low-fluidity PP<2>/high-fluidity PP (inner side)<8>. These PPs had the following MI andmelting point.

[0329] Low-fluidity PP: MI 3 g/10 min, m.p. 147° C.

[0330] High-fluidity PP: MI 7 g/10 min, m.p. 147° C.

[0331] A battery body was inserted into the above armor body, and theassembly was then heat sealed for hermetic sealing to prepare a sampleof Comparative Example A1.

Comparative Example A2

[0332] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by dry lamination. A tray was formed by embossmolding using the laminate thus obtained. An emboss-type armor body wasprepared using this tray and the unmolded laminate as a lid.

[0333] The sealant layer had a single-layer structure of high-fluidityPP.

[0334] High-fluidity PP: MI 20 g/10 min, m.p. 160° C.

[0335] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of ComparativeExample A2.

Comparative Example A3

[0336] 40 μm-thick aluminum not subjected to conversion treatment wasprovided. An oriented nylon film (thickness 25 μm) was laminated ontoone side of the aluminum by dry lamination. Next, a sealant layer waslaminated onto the other side of the aluminum by dry lamination. A traywas formed by emboss molding using the laminate thus obtained. Anemboss-type armor body was prepared using this tray and the unmoldedlaminate as a lid.

[0337] The sealant layer had a three-layer structure of high-fluidity PP{circle over (1)} <1>/low-fluidity PP <8>/high-fluidity PP (inner side){circle over (2)} <1>. These PPs had the following MI and melting point.

[0338] High-fluidity PP {circle over (1)}: MI 10 g/10 min, m.p. 147° C.

[0339] Low-fluidity PP: MI 1 g/10 min, m.p. 160° C.

[0340] High-fluidity PP {circle over (2)}: MI 10, m.p. 147° C.

[0341] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of ComparativeExample A3.

[0342] <Evaluation Method A>

[0343] (1) Short-Circuit Between Lead and Barrier Layer in Armor Body

[0344] The heat sealed part in the lead part was cut, and a photographof the cross section thereof was inspected for short-circuit between thelead part and the armor body. For a sample having a fear ofshort-circuiting between the lead and the barrier layer in the armorbody, contact was examined with a tester, and, when there was no filmbetween the lead and the barrier layer in the armor body in theobservation of a photograph of the cross-section thereof, the sample wasregarded as being in a state just before short-circuiting. A samplewhich had been found to be in a short-circuited state by the tester wasregarded as a short-circuited sample. In this way, the number ofshort-circuited samples was counted.

[0345] (2) Insulating Property

[0346] For each sample, an armor body with one side thereof being openedwas formed. An electrolysis solution was poured into the armor bodythrough the opening. The insulating property was examined in terms ofresistance value in the electrolysis solution and the barrier layer inthe armor body (the barrier layer having been exposed onto the outersurface of the armor body and brought into contact with an electrode).When the resistance value was infinite (∞), the sample was regarded asbeing free from cracks from root cutting.

[0347] Contents: 3 g of a mixed liquid composed of ethylene carbonate,diethyl carbonate, and dimethyl carbonate (1:1:1) which provided 1 MLiPF₆ electrolysis solution.

[0348] (3) Leakage and Delamination

[0349] The heat sealed product was stored at 80° C. for 24 hr and wasinspected for leakage of the contents from the lead part anddelamination of the laminate on the content side.

[0350] Contents: 3 g of a mixed liquid composed of ethylene carbonate,diethyl carbonate, and dimethyl carbonate (1:1:1) which provided 1 MLiPF₆ electrolysis solution.

[0351] (4) Residual Thickness of Heat Sealed Part

[0352] In the cross section of the heat sealed part, after heat sealing,the thickness of the sealant layer (two layers) between the upper andlower barrier layers were measured, and the thickness of the sealantlayer after heat sealing was expressed in terms of residual thickness(percentage retention) by presuming the thickness of the sealant layerbefore heat sealing to be 100.

[0353] <Results A>

Example A

[0354] For Examples A1 to A4, none of short-circuit at the lead part,root cutting, and leakage of contents was observed. Further, there wasno delamination of the laminate. The residual thickness of the heatsealed part was as follows. Example A1 50 Example A2 45 Example A3 60Example A4 45

Comparative Example A

[0355] In Comparative Example A1, neither short-circuit nor delaminationwas observed. The insulation property, however, was 0.1 MΩ, and thephotograph of the cross section showed the presence of cracks.Delamination was not observed.

[0356] In Comparative Example A2, short-circuit was observed. Further,the insulating property was 0.1 MΩ. The photograph of the cross sectionshowed the presence of cracks. Delamination was not observed.

[0357] In Comparative Example A3, there was no short-circuit. For theinsulating property, the resistance value was infinite (∞). Further, thepresence of cracks was not observed. However, delamination occured. Theresidual thickness was as follows. Comparative Example A1 40 ComparativeExample A2 30 Comparative Example A3 60

[0358] <Effect A>

[0359] As is apparent from the above results, in the packaging materialfor a battery according to the present invention, when at least thesealant layer comprises a low-fluidity polypropylene layer having lowsusceptibility to collapse upon exposure to heat and pressure at thetime of heat sealing and a high-fluidity polypropylene layer having highsusceptibility to collapse upon exposure to heat and pressure at thetime of heat sealing and the innermost layer is the high-fluiditypolypropylene layer, at the time of housing a battery body in a pouch oran emboss molded part of the armor body and heat sealing of theperipheral edge of the armor body, the bridged sealant layer functionsas an insulating layer. By virtue of this, the packaging material for abattery can eliminate a fear of causing contact (short-circuit) betweenthe barrier layer in the armor body and the lead and can prevent rootcutting around the heat sealed part, that is, is stable. Further, thelamination of the sealant layer by dry lamination can prevent corrosionof the aluminum face by hydrogen fluoride evolved as a result of areaction of the electrolyte in the battery with water, and, thus, in thearmor body, the delamination of aluminum from the content-side layer canalso be prevented.

[0360] B. Second Aspect of Invention

[0361] The packaging material for a battery according to the secondaspect of the present invention will be described in more detail withreference to the following examples.

[0362] <Common Conditions B>

[0363] Conditions common to Example B and Comparative Example B are asfollows.

[0364] (1) Armor Body

[0365] In the following Example B and Comparative Example B, the size ofa pouch-type armor body was 30 mm in width (inside dimension)×50 mm inlength (inside dimension). In the case of an emboss-type armor body,only one side was embossed, and moldability was evaluated by pressmolding using a mold having a concave (a cavity) having a size of 30mm×50 mm and a depth of 3.5 mm.

[0366] (2) Total Thickness of Sealant Layer

[0367] In all cases, the total thickness of a sealant layer was 30 μm.

[0368] (3) Conversion Treatment

[0369] For both Example B and Comparative Example B, the conversiontreatment of a barrier layer in the armor body was carried out asfollows. An aqueous solution composed of a phenolic resin, achromium(III) fluoride compound, and phosphoric acid was provided as atreatment liquid. The treatment liquid was roll coated onto the barrierlayer, and the coating was baked under conditions such that the filmtemperature was 180° C. or above. The coverage of chromium was 2 mg/m²on a dry weight basis. (3) lead

[0370] (4) Lead and Film for Lead

[0371] For both Example B and Comparative Example B, a lead having athickness of 100 μm, a width of 6 mm, and a length of 25 mm was used.For both Example B and Comparative Example B, a 30-μm acid-modifiedpolypropylene film was provided as a film for a lead, was wound around apredetermined position of the lead for the battery body, and the batterybody was then inserted into the armor body.

[0372] (5) Conditions for Heat Sealing

[0373] Heat sealing was carried out under conditions of 190° C., 1 MPa,and 3 sec.

[0374] However, only for the evaluation of short-circuit, heat sealingwas carried out under conditions of 190° C., 2 MPa, and 5 sec.

Example B1

[0375] Both sides of 20 μm-thick aluminum were subjected to conversiontreatment, and an oriented polyester film (thickness 12 μm) waslaminated onto one conversion treated side of the aluminum by drylamination. Next, the other conversion treated side of the aluminum washeated at a temperature at or above the softening point of acid-modifiedpolypropylene (hereinafter referred to as “PPa”) as an adhesive resinlayer, and PPa was extruded to laminate a multilayered film as a sealantlayer by sandwich lamination. A pillow-type pouch as an armor body wasformed using the laminate thus obtained.

[0376] The sealant layer had a two-layer structure of low-fluidity PP<6>/high-fluidity PP (inner side)<4>. These PPs had the following MI andmelting point. Figures in brackets indicate layer thickness ratio incoextruded multilayer. This is true of Example B and Comparative ExampleB which will be described later.

[0377] Low-fluidity PP: MI 0.5 g/10 min, m.p. 160° C.

[0378] High-fluidity PP: MI 30 g/10 min, m.p. 160° C.

[0379] A battery body was inserted into the above armor body, and theassembly was then heat sealed for hermetic sealing to prepare a sampleof Example B1.

Example B2

[0380] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, an emulsion liquid of acid-modified polypropylene was coated ontothe other conversion treated side of the aluminum, and the coating wasdried and further baked at a temperature of 180° C. Thereafter, asealant layer was laminated onto the surface of the baked layer by hotlamination. A tray was formed by emboss molding using the laminate thusobtained. An emboss-type armor body was prepared using this tray and theunmolded laminate as a lid.

[0381] The sealant layer had a two-layer structure of low-fluidity PP<9>/high-fluidity PP (inner side)<1>. These PPs had the following MI andmelting point.

[0382] Low-fluidity PP: MI 3 g/10 min, m.p. 147° C.

[0383] High-fluidity PP: MI 7 g/10 min, m.p. 147° C.

[0384] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of Example B2.

Example B3

[0385] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by sandwich lamination using acid-modifiedpolypropylene as an adhesive resin. The laminate thus obtained washeated at a temperature at or above the softening point of acid-modifiedpolypropylene and was then subjected to emboss molding to form a tray.An emboss-type armor body was prepared using this tray and the unmoldedlaminate as a lid.

[0386] The sealant layer had a three-layer structure of high-fluidity PP{circle over (1)} <1>/low-fluidity PP <8>/high-fluidity PP (inner side){circle over (2)} <1>. These PPs had the following MI and melting point.

[0387] High-fluidity PP {circle over (1)}: MI 10 g/10 min, m.p. 147° C.

[0388] Low-fluidity PP: MI 1 g/10 min, m.p. 160° C.

[0389] High-fluidity PP {circle over (1)}: MI 10 g/10 min, m.p. 147° C.

[0390] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of Example B3.

Example B4

[0391] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by coextrusion lamination using acid-modifiedpolypropylene as an adhesive resin. The laminate thus obtained washeated at a temperature at or above the softening point of acid-modifiedpolypropylene. A tray was then formed by emboss molding using the heatedlaminate. An emboss-type armor body was prepared using this tray and theunmolded laminate as a lid.

[0392] The sealant layer had a three-layer structure of high-fluidity PP{circle over (1)} <1>/low-fluidity PP <6>/high-fluidity PP (inner side){circle over (1)} <3>. These PPs had the following MI and melting point.

[0393] High-fluidity PP {circle over (1)}: MI 20 g/10 min, m.p. 160° C.

[0394] Low-fluidity PP: MI 3 g/10 min, m.p. 160° C.

[0395] High-fluidity PP {circle over (1)}: MI 89/10 min, m.p. 147° C.

[0396] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of Example B4.

Comparative Example B1

[0397] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, an emulsion liquid of acid-modified polypropylene was coated ontothe other conversion treated side of the aluminum, and the coating wasdried and further baked at a temperature of 180° C. Thereafter, asealant layer was laminated onto the surface of the baked layer by hotlamination. A tray was formed by emboss molding using the laminate thusobtained. An emboss-type armor body was prepared using this tray and theunmolded laminate as a lid.

[0398] The sealant layer had a two-layer structure of low-fluidity PP<2>/high-fluidity PP (inner side)<8>. These PPs had the following MI andmelting point.

[0399] Low-fluidity PP: MI 3 g/10 min, m.p. 147° C.

[0400] High-fluidity PP: MI 7 g/10 min, m.p. 147° C.

[0401] A battery body was inserted into the armor body, followed by heatsealing for hermetic sealing to prepare a sample of Comparative ExampleB1.

Comparative Example B2

[0402] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminatedonto one conversion treated side of the aluminum by dry lamination.Next, a sealant layer was laminated onto the other conversion treatedside of the aluminum by sandwich lamination using acid-modifiedpolypropylene as an adhesive resin. The laminate thus obtained washeated at a temperature at or above the softening point of acid-modifiedpolypropylene and was then subjected to emboss molding to form a tray.An emboss-type armor body was prepared using this tray and the unmoldedlaminate as a lid.

[0403] The sealant layer had a single-layer structure of high-fluidityPP.

[0404] High-fluidity PP: MI 20 g/10 min, m.p. 160° C.

[0405] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of ComparativeExample B2.

Comparative Example B3

[0406] 40 μm-thick aluminum not subjected to conversion treatment wasprovided, and an oriented nylon film (thickness 25 μm) was laminatedonto one side of the aluminum by dry lamination. Next, a sealant layerwas laminated by coextrusion lamination using acid-modifiedpolypropylene as an adhesive resin onto the other side of the aluminum.The laminate thus obtained was heated at a temperature at or above thesoftening point of acid-modified polypropylene and was then subjected toemboss molding to form a tray. An emboss-type armor body was preparedusing this tray and the unmolded laminate as a lid.

[0407] The sealant layer had a single-layer structure of high-fluidityPP, three layers, i.e., {circle over (1)} <1>/low-fluidity PP<8>/high-fluidity PP (inner side) {circle over (2)} <1>. These PPs hadthe following MI and melting point.

[0408] High-fluidity PP {circle over (1)}: MI 10 g/10 min, m.p. 147° C.

[0409] Low-fluidity PP: MI 1 g/10 min, m.p. 160° C.

[0410] High-fluidity PP {circle over (2)}: MI 10 g/10 min, m.p. 147° C.

[0411] A battery body was placed in the tray in the armor body, and thetray was then covered with the lid. The peripheral edge of the tray washeat sealed for hermetic sealing to prepare a sample of ComparativeExample B3.

[0412] <Evaluation Method B>

[0413] (1) Short-Circuit Between Lead and Barrier Layer in Armor Body

[0414] The heat sealed part in the lead part was cut, and a photographof the cross section thereof was inspected for short-circuit between thelead part and the armor body. For a sample having a fear ofshort-circuiting between the lead and the barrier layer in the armorbody, contact was examined with a tester, and, when there was no filmbetween the lead and the barrier layer in the armor body in theobservation of a photograph of the cross section thereof, the sample wasregarded as being in a state just before short-circuiting. A samplewhich had been found to be in a short-circuited state by the tester wasregarded as a short-circuited sample. In this way, the number ofshort-circuited samples was counted.

[0415] (2) Insulating Property

[0416] For each sample, an armor body with one side thereof being openedwas formed. An electrolysis solution was poured into the armor bodythrough the opening. The insulating property was examined in terms ofresistance value in the electrolysis solution and the barrier layer inthe armor body (the barrier layer having been exposed onto the outersurface of the armor body and brought into contact with an electrode).When the resistance value was infinite (∞), the sample was regarded asbeing free from cracks from root cutting.

[0417] Contents: 3 g of a mixed liquid composed of ethylene carbonate,diethyl carbonate, and dimethyl carbonate (1:1:1) which provided 1 MLiPF₆ electrolysis solution.

[0418] (3) Leakage and Delamination

[0419] The heat sealed product was stored at 80° C. for 24 hr and wasinspected for leakage of the contents from the lead part anddelamination of the laminate on the content side.

[0420] Contents: 3 g of a mixed liquid composed of ethylene carbonate,diethyl carbonate, and dimethyl carbonate (1:1:1) which provided 1 MLiPF₆ electrolysis solution.

[0421] (4) Residual Thickness of Heat Sealed Part

[0422] In the cross section of the heat sealed part, after heat sealing,the thickness of the sealant layer (two layers) between the upper andlower barrier layers were measured, and the thickness of the sealantlayer after heat sealing was expressed in terms of residual thickness(percentage retention) by presuming the thickness of the sealant layerbefore beat sealing to be 100.

[0423] <Results B>

[0424] For Examples B1 to B4, none of short-circuit at the lead part,root cutting, and leakage of contents was observed. Further, there wasno delamination of the laminate. The residual thickness of the heatsealed part was as follows. Example B1 52 Example B2 45 Example B3 60Example B4 45

[0425] In Comparative Example B1, neither short-circuit nor delaminationwas observed. The insulating property, however, was 0.1 MΩ, and thephotograph of the cross section showed the presence of cracks. InComparative Example B2, short-circuit was observed. Further, theinsulating property was 0.1 MΩ. The photograph of the cross sectionshowed the presence of cracks. Delamination was not observed. InComparative Example B3, there was no short-circuit. For the insulatingproperty, the resistance value was infinite (∞). Further, the presenceof cracks was not observed. However, delamination occured. The residualthickness was as follows. Comparative Example B1 40 Comparative ExampleB2 30 Comparative Example B3 60

[0426] <Effect B>

[0427] As is apparent from the above results, in the packaging materialfor forming an armor body for a battery according to the second aspectof the present invention, the armor body being adapted for use in such amanner that a battery body is inserted into the armor body and theperipheral edge of the armor body is then heat sealed for hermeticsealing, the packaging material being a laminate comprising at least asubstrate layer, an adhesive layer, a barrier layer, an adhesive resinlayer, and a sealant layer, when at least the sealant layer comprises alow-fluidity polypropylene layer having low susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing and ahigh-fluidity polypropylene layer having high susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing and theinnermost layer is the high-fluidity polypropylene layer, in housing abattery body in a pouch or emboss molded part in the armor body and thenheat sealing the peripheral edge of the armor body to hermetically sealthe assembly, the low-fluidity polypropylene layer functions as aninsulating layer. By virtue of this, the packaging material for abattery can eliminate a fear of causing contact (short-circuit) betweenthe barrier layer in the armor body and the lead and can prevent rootcutting around the heat sealed part.

[0428] Further, since the sealant layer is formed by sandwich laminationor coextrusion lamination through an adhesive resin layer and heating iscarried out at the time of or after the formation of the laminate, thecorrosion of the aluminum face by hydrogen fluoride evolved as a resultof a reaction of an electrolyte in the battery with water can beprevented, and, thus, in the armor body, delamination of aluminum fromthe content-side layer can also be prevented.

[0429] C. Third Aspect of Invention

[0430] The packaging material for a battery according to the thirdaspect of the present invention will be described in more detail withreference to the following examples.

[0431] <Common Conditions C>

[0432] (1) Construction of Packaging Material for Battery

[0433] For both Example C and Comparative Example C, the pouch type andthe emboss type had the following basic construction. The composition ofthe adhesive resin layer, the lamination method, etc. in Example C andthose in Comparative Example C were as described below.

[0434] (Pouch type)

[0435] PET 12/DL 3/ALM 20/conversion treatment/adhesive resin layer15/sealant layer 30

[0436] (Emboss type)

[0437] ON 25 μm/DL 3 μm/conversion treatment/ALM 40 μm/conversiontreatment/adhesive resin layer 15 μm/sealant layer 30 μm

[0438] [Abbreviation PET: biaxially oriented polyester film, ON:biaxially oriented nylon film, ALM: aluminum, DL: dry laminate, and ALM:aluminum]

[0439] The acid-modified polypropylene was unsaturated carboxylicacid-grafted random propylene. In all cases, the sealant layer was afilm or extruded layer of a random polypropylene resin. In Example C andComparative Example C, when the adhesive resin is a blend resin, theblending ratio is by weight.

[0440] (2) Conversion Treatment

[0441] For both Example C and Comparative Example C, the conversiontreatment of a barrier layer in the armor body was carried out asfollows. An aqueous solution composed of a phenolic resin, achromium(III) fluoride compound, and phosphoric acid was provided as atreatment liquid. The treatment liquid was roll coated onto the barrierlayer, and the coating was baked under conditions such that the filmtemperature was 180° C. or above. The coverage of chromium was 1 mg/m²on a dry weight basis.

[0442] (3) Type of Armor Body

[0443] In the case of the pouch type, a pillow type having a size of 30mm in width (inside dimension)×50 mm in length (inside dimension) wasused for evaluation. In the case of the emboss type, one-side embosstype was prepared, and the moldability was evaluated by press moldingusing a mold having a concave (a cavity) having a size of 30 mm×50 mmand a depth of 3.5 mm. In all examples of the emboss type, the embossedlaminate not subjected to molding was used as a lid.

[0444] (4) Conditions for Heat Sealing

[0445] 190° C., 1.0 MPa, 3 sec

Example C1

[0446] One side of 20 μm-thick aluminum was subjected to conversiontreatment, and an oriented polyester film (thickness 12 μm) waslaminated by dry lamination onto the aluminum in its side not subjectedto conversion treatment. Next, the conversion treated side of thealuminum was heated at a temperature at or above the softening point ofa polypropylene resin as an adhesive resin by far infrared radiation andhot air. In this state, a 15 μm-thick adhesive resin, which will bedescribed later, was extruded to laminate a 30 μm-thick polypropylenefilm as a sealant layer by sandwich lamination.

[0447] The adhesive resin was a blend of 60 parts of polypropylene (MI26 g/10 min) with 40 parts of acid-modified polypropylene (MI 1.0 g/10min). The MI value of the blend resin was 5 g/10 min. A pouch-type armorbody was formed using the laminate thus obtained.

Example C2

[0448] One side of 20 m-thick aluminum was subjected to conversiontreatment, and an oriented polyester film (thickness 12 μm) waslaminated by dry lamination onto the aluminum in its side not subjectedto conversion treatment. Next, an adhesive resin (15 μm), which will bedescribed later, and a polypropylene resin (30 μm) as a sealant layerwere coextruded and laminated onto the conversion treated side of thealuminum. The laminate thus obtained was then heated at a temperature ator above the softening point of the adhesive resin.

[0449] The adhesive resin was a blend of 90 parts of high-MIacid-modified polypropylene with 10 parts of low-density polyethylene.The MI value of the adhesive resin was 18 g/10 min.

[0450] A pouch-type armor body was formed using the laminate thusobtained.

Example C3

[0451] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminated bydry lamination onto one side of the conversion treated aluminum. Next,the other conversion treated side of the aluminum was heated at atemperature at or above the softening point of a polypropylene resin asan adhesive resin by far infrared radiation and hot air. In this state,a 15 μm-thick adhesive resin, which will be described later, wasextruded to laminate a 30 μm-thick polypropylene film as a sealant layerby sandwich lamination.

[0452] The adhesive resin was a blend of 74 parts of polypropylene (MI26 g/10 min) with 26 parts of acid-modified polypropylene (MI 1.0 g/10min). The MI value of the blend resin was 5 g/10 min.

[0453] A tray was formed by emboss molding using the laminate thusobtained. An armor body was prepared using this tray and the unmoldedlaminate as a lid material.

Example C4

[0454] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminated bydry lamination onto one side of the conversion treated aluminum. Next, a15 μm-thick adhesive resin, which will be described later, was extrudedto laminate a 30 μm-thick polypropylene film as a sealant layer bysandwich lamination onto the other conversion treated side of thealuminum. The laminate thus obtained was then heated at a temperature ator above the softening point of the adhesive resin.

[0455] The adhesive resin was a blend of 80 parts of acid-modifiedpolypropylene, 10 parts of LDPE, 10 parts of butadiene, and 10 parts ofbutadiene. The MI value of the adhesive resin was 9 g/10 min.

[0456] A tray was formed by emboss molding using the heated laminate. Anarmor body was prepared using this tray and the unmolded laminate as alid material.

Example C5

[0457] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminated bydry lamination onto one side of the conversion treated aluminum. Next,the other conversion treated side of the aluminum was heated at atemperature at or above the softening point of a polypropylene resin asan adhesive resin by far infrared radiation and hot air. In this state,an adhesive resin (15 μm), which will be described later, and apolypropylene resin (30 μm) as a sealant layer were coextruded andlaminated onto the aluminum.

[0458] The adhesive resin was a blend of 80 parts of acid-modifiedpolypropylene, 10 parts of LDPE, 5 parts of butadiene, and 5 parts of anethylene-propylene copolymer. The MI value of the adhesive resin was 12g/10 min. A tray was formed by emboss molding using the laminate thusobtained. An armor body was prepared using this tray and the unmoldedlaminate as a lid material.

Comparative Example C1

[0459] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminated bydry lamination onto one side of the conversion treated aluminum. Next,the other conversion treated side of the aluminum was heated at atemperature at or above the softening point of a polypropylene resin asan adhesive resin by far infrared radiation and hot air. In this state,a 15 μm-thick adhesive resin, which will be described later, wasextruded to laminate a 30 μm-thick polypropylene film as a sealant layerby sandwich lamination.

[0460] The adhesive resin was acid-modified polypropylene (MI 0.1 g/10min).

[0461] A tray was formed by emboss molding using the laminate thusobtained. An armor body was prepared using this tray and the unmoldedlaminate as a lid material.

Comparative Example C2

[0462] Both sides of 40 μm-thick aluminum were subjected to conversiontreatment, and an oriented nylon film (thickness 25 μm) was laminated bydry lamination onto one side of the conversion treated aluminum. Next, a15 μm-thick adhesive resin, which will be described later, was extrudedto laminate a 30 μm-thick polypropylene film as a sealant layer bysandwich lamination onto the other conversion treated side of thealuminum. The laminate thus obtained was then heated at a temperature ator above the softening point of the adhesive resin.

[0463] The adhesive resin was a blend of 90 parts of acid-modifiedpolypropylene and 10 parts of LDPE. The MI value of the adhesive resinwas 25.

[0464] A tray was formed by emboss molding using the heated laminate. Anarmor body was prepared using this tray and the unmolded laminate as alid material.

Comparative Example C3

[0465] 40 μm-thick aluminum not subjected to conversion treatment wasprovided. An oriented nylon film (thickness 25 μm) was laminated by drylamination onto one side of the aluminum. Next, a 30 μm-thickpolypropylene film as a sealant layer was laminated by sandwichlamination using a resin, which will be described later, as an adhesiveresin (15 μm) onto the other side of the aluminum. The laminate thusobtained was then heated at a temperature at or above the softeningpoint of the adhesive resin.

[0466] The adhesive resin was a blend of 80 parts of acid-modifiedpolypropylene, 10 parts of LDPE, and 10 parts of butadiene. The MI valueof the adhesive resin was 9 g/10 min.

[0467] A tray was formed by emboss molding using the heated laminate. Anarmor body was prepared using this tray and the unmolded laminate as alid material.

[0468] <Evaluation Item C>

[0469] 1) Root Cutting at Sealed Part

[0470] A battery body was housed in the armor body, followed by hermeticsealing. The cross section of the sealed part and the nonsealed partcontinued to the sealed part was observed under a microscope for rootcutting at the adhesive resin layer portion

[0471] 2) Percentage Retention of Thickness of Heat Seal LKayer(Adhesive Resin Layer and Sealant layer)

[0472] After heat sealing, the thickness of the heat seal layer wasmeasured, and the proportion of the thickness of the heat seal layerafter heat sealing relative to the total thickness of the heat seallayer before heat sealing was calculated.

[0473] 3) Delamination

[0474] 3 g of a mixed liquid composed of ethylene carbonate, diethylcarbonate, and dimethyl carbonate (1:1:1), which provided 1 M LiPF₆, wasfilled into the armor body, and the armor body was held at a temperatureof 85° C. for 7 days. Thereafter, visual inspection was carried out fordelamination between ALM and the adhesive resin layer.

[0475] <Results C>

Example C

[0476] Neither root cutting at the sealed part nor delamination betweenALM and the adhesive resin layer was observed for Examples C1 to C5(number of samples: 100 for each evaluation item).

[0477] The percentage retention of the thickness of the heat seal layerwas as follows. Example C1 60% Example C2 32% Example C3 70% Example C460% Example C5 55%

Comparative Example C

[0478] For Comparative Example C1, neither root cutting at the sealedpart nor delamination between ALM and the adhesive resin layer wasobserved (number of samples: 100 for each evaluation item). In theemboss molding, however, cracking of ALM occurred in 25 samples out of100 samples.

[0479] For Comparative Example C2, heat sealing resulted in reducedthickness of the heat seal layer, and root cutting occurred in 3 samplesout of 100 samples. Delamination between ALM and the adhesive resinlayer was not observed.

[0480] For Comparative Example C3, root cutting was not observed.However, delamination between ALM and the adhesive resin layer occurredin 54 samples out of 100 samples. The percentage retention of thethickness of the heat seal layer in Comparative Example C was asfollows. Comparative Example C1 75% Comparative Example C2 22%Comparative Example C3 60%

[0481] <Effect C>

[0482] In a packaging material for forming an armor body for a battery,the armor body being adapted for use in such a manner that a batterybody is inserted into the armor body and the peripheral edge of thearmor body is then heat sealed for hermetic sealing, when the packagingmaterial is a laminate comprising at least a substrate layer, anadhesive layer, aluminum, a conversion treated layer, an adhesive resinlayer, and a polypropylene resin-based sealant layer and the adhesiveresin layer is formed of a resin having a melt index in the range of 5to 20 g/10 min, the effect of preventing short-circuit between thebarrier layer and the lead can be attained. Further, the formation of aresin pool around the inner edge of the sealed part and root cuttingcaused at the end of resin pool can be prevented.

[0483] D. Fourth Aspect of Invention

[0484] The packaging material for a battery according to the fourthaspect of the present invention will be described in more detail withreference to the following examples.

[0485] <Common Conditions D>

[0486] Conditions common to Example D and Comparative Example D were asfollows.

[0487] (1) Armor Body

[0488] In all cases, the armor body was of emboss type and had aconstruction of oriented nylon 25 μm/adhesive layer (1)/conversiontreated layer/ALM 40 μm/conversion treated layer/adhesive layer(2)/sealant layer 30 μm. The laminates used in Example D and ComparativeExample D were produced by lamination according to the following methodunless otherwise specified.

[0489] A conversion treated layer was formed by chromate treatment onboth sides of aluminum (thickness 40 μm). An oriented nylon film(thickness 25 μm) was laminated by dry lamination onto one side of thealuminum with the conversion treated layer formed on its both sides toform an adhesive layer (1). An adhesive layer (2) was formed on theother side of the aluminum by a method indicated in Example D andComparative Example D, and a sealant layer (thickness 30 μm) waslaminated to prepare a laminate.

[0490] For both Example D and Comparative Example D, the chromatetreatment was carried out by roll coating an aqueous solution containinga phenolic resin, a chromium(III) fluoride compound, and phosphoric acidas a treatment liquid and baking the coating under conditions forbringing the film temperature to 180° C. or above. The coverage ofchromium was 2 mg/m² on a dry weight basis.

[0491] Next, a tray was formed by emboss molding using the laminate thusobtained. An armor body was prepared using this tray and the unmoldedlaminate as a lid.

[0492] (2) Type of Armor Body

[0493] In all cases, the armor body was of one-side emboss type. For themold for emboss molding for the formation of the tray, the size of theconcave portion (cavity) was 30 mm×50 mm, and the molding depth wasregulated in increments of 0.5 mm by regulating the intrusion level ofthe convex portion.

[0494] (3) Abbreviations

[0495] Abbreviations used in the following description are as follows.

[0496] Main Resins

[0497] ON: oriented nylon film

[0498] ALM: aluminum foil

[0499] LL: conventional linear low-density polyethylene with density of0.925

[0500] MLL1: metallocene LLDPE with density of 0.92

[0501] MLL2: metallocene LLDPE with density of 0.90

[0502] MD: medium-density polyethylene with density of 0.93

[0503] LD: low-density polyethylene with density of 0.90

[0504] PEa: acid-modified polyethylene

[0505] PEaH: acid-modified polyethylene emulsion

Example D1

[0506] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination, and a film as a sealant layer waslaminated onto the other conversion treated side of ALM by drylamination to prepare a laminate of Example D1.

[0507] The film as the sealant layer had a two-layer structure of LL(thickness 25 μm), provided on the laminate side, and MLL1 (thickness 5μm) provided on the inner side.

Example D2

[0508] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination, and a film as a sealant layer waslaminated onto the other conversion treated side of ALM by drylamination to prepare a laminate of Example D2.

[0509] The film as the sealant layer had a single-layer structure ofMLL1 (thickness 30 μm).

Example D3

[0510] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. 15 μm-thick PEa as an adhesiveresin was extruded to laminate a 30-μm sealant layer film onto the otherconversion treated side of ALM by sandwich lamination. The laminate thusobtained was heated at a temperature at or above the softening point ofPEa to prepare a laminate of Example D3.

[0511] The film as the sealant layer had a two-layer structure of LL(thickness 25 μm), provided on the laminate side, and MLL1 (thickness 5μm) provided on the inner side.

Example D4

[0512] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. The other conversion treated sideof ALM was heated at a temperature at or above the softening point ofPEa, and 15 μm-thick PEa as an adhesive resin was extruded to laminate a30-μm sealant layer film by sandwich lamination to prepare a laminate ofExample D4.

[0513] The film as the sealant layer had a two-layer structure of MD(thickness 10 μm), provided on the laminate side, and a resin blend(thickness 20 μm) of MLL2 and MD (blending weight ratio: MLL2: MD=9:1)provided on the inner side.

Example D5

[0514] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. The other conversion treated sideof ALM was heated at a temperature at or above the softening point ofPEa, and 15 μm-thick PEa as an adhesive resin was extruded to laminate a30-μm sealant layer film by sandwich lamination to prepare a laminate ofExample D5.

[0515] The film as the sealant layer had a single-layer structure ofMLL1 (thickness 30 μm).

Example D6

[0516] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. PEa (15 μm) as an adhesive resinand a resin for a sealant layer (30 μm) were coextruded and laminatedonto the other conversion treated side of ALM. The laminate thusobtained was heated at a temperature at or above the softening point ofPEa to prepare a laminate of Example D6.

[0517] The resin for the sealant layer was a resin blend of MLL1 and LD(blending weight ratio: MLL1: LD=7:3).

Example D7

[0518] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. PEa as an adhesive resin wasextruded on the other conversion treated side of ALM. Subsequently, aresin for a sealant layer (30 μm) was extruded, and the laminate thusobtained was heated at a temperature at or above the softening point ofPEa to prepare a laminate of Example D7.

[0519] The resin for the sealant layer was a resin blend of MLL1 and LD(blending weight ratio: MLL1: LD=7:3).

Example D8

[0520] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. PEa as an adhesive resin wasextruded on the other conversion treated side of ALM. The intermediatelaminate thus obtained was then heated at a temperature at or above thesoftening point of PEa, and a resin for a sealant layer (30 μm) was thenextruded to prepare a laminate of Example D8.

[0521] The resin for the sealant layer was a resin blend of MLL1 and LL(blending weight ratio: MLL1: LL=8:2).

Example D9

[0522] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. PEaH was roll coated onto theother conversion treated side of ALM, and the coating was dried and heatbaked, followed by hot lamination of a film as a sealant layer onto thebaked layer to prepare a laminate of Example D9.

[0523] The film as the sealant layer was MLL1 (thickness 30 μm).

Comparative Example D1

[0524] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination, and a film as a sealant layer waslaminated onto the other conversion treated side of ALM by drylamination to prepare a laminate of Comparative Example D1.

[0525] The film as the sealant layer had a single-layer structure of LL(thickness 30 μm).

Comparative Example D2

[0526] ALM (thickness 40 μm) both sides of which had not been subjectedto conversion treatment was provided. ON (thickness 25 μm) was laminatedonto one side of ALM by dry lamination, and a film as a sealant layerwas laminated onto the other side of ALM by dry lamination to prepare alaminate of Comparative Example D2.

[0527] The film as the sealant layer had a single-layer structure ofMLL1 (thickness 30 μm).

Comparative Example D3

[0528] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. 15 μm-thick PEa as an adhesiveresin was extruded to laminate a 30-μm film for a sealant layer onto theother conversion treated side of ALM by sandwich lamination. Thelaminate thus obtained was heated at a temperature at or above thesoftening point of PEa to prepare a laminate of Comparative Example D3.

[0529] The film as the sealant layer was LL (thickness 30 μm).

Comparative Example D4

[0530] ALM (thickness 40 μm) not subjected to conversion treatment wasprovided. ON (thickness 25 μm) was laminated onto one side of ALM by drylamination. 15 μm-thick PEa as an adhesive resin was extruded tolaminate a 30-μm film for a sealant layer onto the other side of ALM bysandwich lamination. The laminate thus obtained was heated at atemperature at or above the softening point of PEa to prepare a laminateof Comparative Example D4.

[0531] The film as the sealant layer had a two-layer structure of LL(thickness 25 μm) on the laminate side and MLL1 (thickness 5 μm) on theinner side.

Comparative Example D5

[0532] Both sides of ALM (thickness 40 μm) were subjected to conversiontreatment. ON (thickness 25 μm) was laminated onto one conversiontreated side of ALM by dry lamination. PEaH was roll coated onto theother conversion treated side of ALM, and the coating was dried and heatbaked, followed by hot lamination of a film as a sealant layer onto thebaked layer to prepare a laminate of Comparative Example D5.

[0533] The film as the sealant layer was LL (thickness 30 μm).

[0534] <Evaluation Method D>

[0535] (1) Delamination

[0536] An electrolysis solution was filled into each armor body formedusing the laminates prepared in the examples and comparative examples.The assembly was then stored at 60° C. for 24 hr in the case where thelaminate was prepared by dry lamination, while the assembly was storedat 85° C. for 24 hr in the case where the laminate was prepared byextrusion lamination using an adhesive resin. Thereafter, the assemblieswere inspected for delamination of the aluminum (conversion treatedlayer) from the adhesive layer.

[0537] Electrolysis solution: 3 g of a mixed liquid composed of ethylenecarbonate, diethyl carbonate, and dimethyl carbonate (volumeratio=1:1:1), which provided 1 M LiPF₆.

[0538] (2) Moldability

[0539] For each of Example D and Comparative Example D, 50 trays wereformed by molding to determine the molding intrusion level (mm) forstably providing trays free from pinholes, wrinkles, and whitening.

[0540] (3) Sealing Strength

[0541] After hermetic sealing under conditions of 190° C., surfacepressure of 1.0 MPa, and 3.0 sec, the peel strength at the sealed partwas measured. Unit: N/15 mm.

[0542] <Results D>

Example D

[0543] For Examples D1 to D9, delamination did not occur. Regarding themoldability, the trays formed by molding were free from pinholes,wrinkles and the like, that is, the moldability was good. The seal inthe heat sealed part also had stable strength. For Example D, themoldability and the sealing strength were as follows. Molding depthSealing strength Example D1 5.0 12 Example D2 5.5 12 Example D3 4.5 13Example D4 4.0 11 Example D5 5.0 13 Example D6 4.5 11 Example D7 4.5 11Example D8 5.0 12 Example D9 5.0 12

Comparative Example D

[0544] For Comparative Example D1, delamination did not occur, and themoldability was also good. However, the sealing strength was low. ForComparative Example D2 and Comparative Example D4, delaminationoccurred, although there was no problem of moldability and sealingstrength.

[0545] For Comparative Example D3 and Comparative Example D5, thesealing strength was low, although delamination did not occur and themoldability was also good.

[0546] The moldability and the sealing strength for Comparative ExampleD were as follows. Molding depth Sealing strength Comparative Example D14.5 9 Comparative Example D2 5.5 12 Comparative Example D3 4.0 9Comparative Example D4 4.5 13 Example D5 5.0 8

[0547] <Effect D>

[0548] In the packaging material for a battery, when at least thesealant layer or the innermost layer in the sealant layer is formed of ametallocene LLDPE resin or a metallocene LLDPE-blended resin, themoldability at the time of emboss molding could be improved over that inthe case of conventional LLDPE and, consequently, the occurrence ofwrinkles and pinholes could be prevented. Further, the sealing strengthwas advantageously higher than that in the case of conventional LLDPE.In the armor body, when the conversion treatment is carried out on bothsides of aluminum, the occurrence of delamination between the substratelayer and the aluminum can be prevented at the time of emboss moldingand at the time of heat sealing. When the sealant layer is formed by drylamination, hot lamination, sandwich lamination, or coextrusionlamination, heating at the time of or after the formation of thelaminate can prevent the corrosion of the aluminum face by hydrogenfluoride evolved as a result of a reaction of an electrolyte in thebattery with water and, thus, can also prevent delamination of aluminumfrom the content-side layer.

1. A packaging material for forming an armor body for a battery, saidarmor body being adapted for use in such a manner that a battery body isinserted into the armor body and the peripheral edge of the armor bodyis then heat sealed for hermetic sealing, said packaging material beinga laminate comprising at least a substrate layer, an adhesive layer, abarrier layer, a dry laminate layer, and a sealant layer, characterizedin that at least the sealant layer comprises a low-fluiditypolypropylene layer having low susceptibility to collapse upon exposureto heat and pressure at the time of heat sealing and a high-fluiditypolypropylene layer having high susceptibility to collapse upon exposureto heat and pressure at the time of heat sealing, and the innermostlayer is the high-fluidity polypropylene layer.
 2. The packagingmaterial for a battery according to claim 1, characterized in that thebarrier layer comprises at least a conversion treated layer provided onits dry laminate layer side.
 3. The packaging material for a batteryaccording to claim 1 or 2, characterized in that the sealant layer has atwo-layer structure of the low-fluidity polypropylene layer and thehigh-fluidity polypropylene layer and the high-fluidity polypropylenelayer is the innermost layer.
 4. The packaging material for a batteryaccording to claim 1 or 2, characterized in that the sealant layer has athree-layer structure of the high-fluidity polypropylene layer, thelow-fluidity polypropylene layer, and the high-fluidity polypropylenelayer.
 5. The packaging material for a battery according to any one ofclaims 1 to 4, characterized in that a film for a lead is interposedbetween the armor body for a battery and a lead part in the batterybody.
 6. A packaging material for forming an armor body for a battery,said armor body being adapted for use in such a manner that a batterybody is inserted into the armor body and the peripheral edge of thearmor body is then heat sealed for hermetic sealing, said packagingmaterial being a laminate comprising at least a substrate layer, anadhesive layer, a barrier layer, an adhesive resin layer, and a sealantlayer, characterized in that at least the sealant layer comprises alow-fluidity polypropylene layer having low susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing and ahigh-fluidity polypropylene layer having high susceptibility to collapseupon exposure to heat and pressure at the time of heat sealing, and theinnermost layer is the high-fluidity polypropylene layer.
 7. Thepackaging material for a battery according to claim 6, characterized inthat the barrier layer comprises at least a conversion treated layerprovided on its adhesive resin layer side.
 8. The packaging material fora battery according to claim 6 or 7, characterized in that the sealantlayer has a two-layer structure of the low-fluidity polypropylene layerand the high-fluidity polypropylene layer and the high-fluiditypolypropylene layer is the innermost layer.
 9. The packaging materialfor a battery according to claim 6 or 7, characterized in that thesealant layer has a three-layer structure of the high-fluiditypolypropylene layer, the low-fluidity polypropylene layer, and thehigh-fluidity polypropylene layer.
 10. The packaging material for abattery according to any one of claims 6 to 9, characterized in that theadhesive resin layer is a baked layer of an emulsion of an acid-modifiedpolyolefin, and the sealant layer has been adhered to the baked layer byheat lamination.
 11. The packaging material for a battery according toany one of claims 6 to 10, characterized in that the adhesive resinlayer is formed of acid-modified polypropylene and the sealant layer hasbeen previously formed and has been stacked onto the adhesive resinlayer by sandwich lamination.
 12. The packaging material for a batteryaccording to any one of claims 6 to 10, characterized in that theadhesive resin layer is formed of acid-modified polypropylene and thesealant layer has been stacked onto the adhesive resin layer bycoextrusion lamination.
 13. The packaging material for a batteryaccording to any one of claims 6 to 12, characterized in that anadhesive film is interposed between the armor body for a battery and alead part in the battery body.
 14. A packaging material for forming anarmor body for a battery, said armor body being adapted for use in sucha manner that a battery body is inserted into the armor body and theperipheral edge of the armor body is then heat sealed for hermeticsealing, said packaging material being a laminate comprising at least asubstrate layer, an adhesive layer, aluminum, a conversion treatedlayer, an adhesive resin layer, and a polypropylene resin-based sealantlayer, characterized in that the adhesive resin layer is formed of aresin having a melt index in the range of 5 to 20 g/10 min.
 15. Thepackaging material for a battery according to claim 14, characterized inthat the adhesive resin layer comprises a polypropylene resin.
 16. Thepackaging material for a battery according to claim 14 or 15,characterized in that the adhesive resin layer comprises acid-modifiedpolypropylene.
 17. The packaging material for a battery according toclaim 14, characterized in that the adhesive resin layer comprises anacid-modified polypropylene resin and, added to the acid-modifiedpolypropylene resin, at least one component selected from a low-densitypolyethylene resin, a low crystalline ethylene-butene-propylenecopolymer with a density of 900 kg/M³, a noncrystallineethylene-propylene copolymer, a propylene-α-olefin copolymer, and arubber component.
 18. The packaging material for a battery according toclaim 14, characterized in that the adhesive resin layer is formed of ablend of at least two polypropylene resins with different melt indexes.19. The packaging material for a battery according to claim 18,characterized in that at least one of the at least two polypropyleneresins constituting the adhesive resin layer is an acid-modifiedpolypropylene resin.
 20. The packaging material for a battery accordingto any one of claims 14 to 19, characterized in that the laminatecomprises at least the substrate layer, the adhesive layer, a conversiontreated layer (1), aluminum, a conversion treated layer (2), theadhesive resin layer, and the polypropylene resin-based sealant layer.21. A battery characterized by comprising a battery body housed andhermetically sealed into an armor body formed of the packaging materialfor a battery according to any one of claims 14 to
 20. 22. A packagingmaterial for forming an armor body for a battery, said armor body beingadapted for use in such a manner that a battery body is inserted intothe armor body and the peripheral edge of the armor body is then heatsealed for hermetic sealing, said packaging material being a laminatecomprising at least a substrate layer, an adhesive layer 1, a barrierlayer, an adhesive layer 2, and a sealant layer, characterized in thatthe sealant layer comprises one resin layer or a laminate of two or moreresin layers comprising metallocene linear low-density polyethylene. 23.The packaging material for a battery according to claim 22,characterized in that the sealant layer is formed of a metallocenelinear low-density polyethylene resin.
 24. The packaging material for abattery according to claim 22, characterized in that the sealant layeris formed of a polyethylene resin containing not less than 10% of ametallocene linear low-density polyethylene resin.
 25. The packagingmaterial for a battery according to claim 22, characterized in that thesealant layer has a multilayer structure comprising at least a layerformed of a metallocene linear low-density polyethylene resin.
 26. Thepackaging material for a battery according to claim 22, characterized inthat the sealant layer has a multilayer structure comprising apolyethylene resin layer containing not less than 10% of a metallocenelinear low-density polyethylene resin.
 27. The packaging material for abattery according to any one of claims 22 to 26, characterized in thatthe adhesive layer 2 has been formed by dry lamination.
 28. Thepackaging material for a battery according to any one of claims 22 to27, characterized in that the adhesive layer 2 is an acid-modifiedpolyolefin coating-baked layer.
 29. The packaging material for a batteryaccording to any one of claims 22 to 27, characterized in that theadhesive layer 2 is an extruded layer of an acid-modified polyolefin.